Engineering 

T  TKr-nrv 


THE  PRACTICE  OF  LUBRICATION 


%  Qraw-MlBook  &.  7m 

PUBLISHERS     OF     BOOKS      FOR_, 

Coal  Age     v     Electric  Railway  Journal 

Electrical  World  ^  Engineering  News -Record 

American  Machinist  ^  Ingenieria  Internacional 

Engineering 8 Mining  Journal      ^     Power 

Chemical  6   Metallurgical  Engineering 

Electrical  Merchandising 


THE  PRACTICE  OF 

LUBRICATION 

AN  ENGINEERING  TREATISE 

ON 

THE  ORIGIN,  NATURE  AND  TESTING  OF  LUBRICANTS, 
THEIR  SELECTION,  APPLICATION  AND  USE 


BY 
T.  C.  THOMSEN,  B.Sc.  (Copenhagen)  M.  I.  Mech.  E.  etc. 

CONSULTING   OIL   ENGINEER,  FOR   MANY   YEARS   CHIEF   ENGINEER   TO   THE  VACUUM    OIL 

COMPANY,   LTD.,  LONDON:    LATE   RESEARCH   ENGINEER  TO   THE 

ANGLO-MEXICAN    PETROLEUM   CO.,    LTD. 


FIIIST  EDITION 


McGRAW-HILL  BOOK  COMPANY,  INC. 

NEW  YORK:    239   WEST  39TH  STREET 

LONDON:    G  &  8  BOUVERIE  ST.,  E.  C.  4 

1920 


PREFACE 

Lubrication  has  for  many  years  received  only  scant  attention 
and  existing  standards  of  lubrication  still  leave  considerable 
room  for  improvement.  Very  few  firms  employ  qualified  chem- 
ists to  assist  them  in  maintaining  a  reasonable  standard  of 
efficiency;  and  such  a  thing  as  technical  service  embodying  a 
highly  trained  staff  of  lubricating  engineers  was  unheard  of 
until  recent  years  and  is  still  considered  an  expensive  luxury  by 
most  firms. 

A  development  is,  however,  gradually  taking  place  in  the 
right  direction.  Both  oil  suppliers  and  oil  users  are  beginning 
to  realize  that  lubrication  can  no  longer  be  left  to  guess  work; 
that  to  send  salesmen  out  with  a  set  of  samples  and  a  price  list, 
but  without  the  necessary  technical  knowledge  or  backing,  is 
to  court  failure;  that  entertaining  customers  or  obtaining  busi- 
ness simply  through  friendship  between  salesman  and  buyer 
is  not  sufficient,  because  friendship  does  not  add  to  the  lubricat- 
ing value  of  the  oil,  nor  does  it  always  help  to  select  the  right 
oil  or  use  it  in  the  right  way. 

Lubrication  is  rapidly  becoming  a  science.  Some  oil  firms 
have  appreciated  the  value  of  the  assistance  of  a  staff  of  qualified 
lubricating  engineers,  who  should  be  able  to  inspect  a  plant,  to 
report  intelligently  on  the  lubrication  conditions  of  all  engines 
and  machinery,  to  point  out  and  estimate  the  value  of  possible 
improvements  in  regard  to  savings  in  power  or  lubricants,  to 
investigate  complaints,  etc.  These  men  should  have  a  thorough 
knowledge  of  their  firms'  products,  so  that  they  can  recommend 
the  correct  grades  for  any  kind  of  machinery,  even  without  know- 
ing anything  about  the  lubricants  actually  in  use. 

Obtaining  samples  for  analysis  and  " matching"  them  at  a 
lower  price  per  gallon  is  unfortunately  still  the  standard  of 
procedure  of  most  oil  firms,  and  should  be  discouraged  by  the 
consumer  in  favor  of  a  more  efficient  lubrication  service,  which 
places  the  supply  of  lubricants  on  a  sound  engineering  basis. 

Large  consumers  of  lubricants  will  find  it  worth  their  while  to 
ask  oil  suppliers  to  demonstrate  the  value  of  their  lubricants; 

vii 


Vlli  PREFACE 

and  they  will  soon  find  that  it  is  of  far  greater  importance  than 
is  generally  realized  that  the  lubricating  systems  of  the  engines 
or  machinery  be  as  perfect  as  possible,  that  the  correct  grades  of 
lubricant  be  selected,  that  the  lubricants  be  stored  and  dis- 
tributed in  the  best  manner,  used  in  the  right  way  and  in  the 
right  amount,  and  that  the  waste  oil,  if  any,  be  collected,  purified 
and  used  again. 

Oil  firms  who  intend  to  develop  a  technical  organization  must 
not  make  the  mistake  of  thinking  that  they  can  engage  any 
kind  of  engineers.  A  high  standard  of  general  engineering 
knowledge  is  essential,  besides  considerable  tact  in  dealing  with 
consumers. 

Furthermore,  an  engineer,  however  excellent  his  general 
knowledge,  does  not  become  a  lubricating  engineer  the  moment 
he  is  engaged  by  an  oil  firm.  He  will  have  to  study  the  available 
literature,  but  must  not  expect  to  develop  his  experience  by 
sitting  in  the  office.  He  should  study  closely  lubrication  of 
machinery  under  actual  working  conditions  to  the  minutest 
details,  and  thus  he  will  in  time  accumulate  the  right  kind  of 
special  knowledge  and  develop  the  right  instinct  to  enable  him 
to  render  first-class  service,  and  to  add  his  effort,  be  it  great  or 
small,  to  the  advancement  of  the  science  of  lubrication. 

The  lubricating  engineer  needs  good  assistance  from  the 
chemical  laboratory  in  analysing  oils,  deposits,  etc.  On  the 
other  hand,  chemists  should  not  be  expected  nor  should  they  be 
allowed  to  make  recommendations,  except  in  consultation  with 
an  engineer,  who  is  able  to  investigate  and  judge  the  importance 
of  the  mechanical  and  operating  conditions  of  the  plant,  which 
is  essential  in  order  to  interpret  correctly  the  value  of  the  labo- 
ratory's findings. 

The  oil  manufacturer,  through  lubricating  engineers,  must 
watch  constantly  the  results  obtained  under  working  conditions 
by  the  various  standard  grades  of  lubricants,  and  he  will  in  this 
way  accumulate  knowledge  as*  to 'the  value  and  range  of  service 
of  each  particular  grade;  he  will  also  find  out  possible  weaknesses 
and  the  engineering  staff  in  conjunction  with  his  chemical  staff 
will  be  able  to  point  the  way  to  remedy. 

Oil  firms  who  have  developed  an  efficient  technical  staff  will 
always  have  a  great  advantage  over  other  firms  who  are  less  well 
equipped.  Their  salesmen  having  the  benefit  of  technical 
assistance  will  easily  command  greater  sales  than  their  com- 
petitors. Even  if  their  products  are  no  better,  they  will  yet  be 
able  to  render  to  their  customers  better  service,  because  they 
know  how  to  select  the  correct  grades,  and  can  indicate  to  the 


PREFACE  ix 

consumer  how  the  maximum  value  of  these  grades  can  be  ob- 
tained. Such  service  always  brings  credit  and  goodwill  to  the 
oil  supplier,  and  demonstrates  to  the  consumer  that  lubrication 
service  comprises  a  great  deal  more  than  is  indicated  by  the 
price  per  gallon. 

The  Chief  Engineer  or  Master  Mechanic  of  a  works  cannot  be 
expected  to  know  everything  there  is  to  know  about  lubrication ; 
it  is  no  discredit  to  him  if  he  gains  a  few  points  by  discussing  the 
lubrication  of  his  plant  with  lubricating  engineers  who  have 
made  a  life  study  of  the  subject. 

The  author  hopes  that  oil  firms  who  have  no  engineering  staff 
will  see  the  necessity  of  developing  a  technical  service,  sufficient 
for  their  needs  in  keeping  with  modern  sales  methods,  which  are 
directed  towards  selling  lubrication,  rather  than  lubricants,  or 
selling  experience  and  knowledge  rather  than  selling  oils  on  a 
price  per  gallon  basis. 

The  subject  of  lubrication  is  intimately  connected  with  the 
mechanical  and  operating  conditions  of  engines  or  machinery. 
The  author  has  therefore  endeavored  to  present  for  each  type  of 
engine  or  class  of  machinery  the  "technical  background,'7  with- 
out which  it  is  futile  to  attempt  to  focus  the  lubricating  problems, 
as  seen  by  the  engineer  or  the  chemist,  and  without  which 
it  is  impossible  to  determine  the  character  of  the  oils  required 
to  give  the  best  service. 

The  author  is  well  aware  of  the  magnitude  of  such  a  task  and 
the  many  shortcomings  of  the  present  work,  but  he  ventures  to 
hope  that  the  way  in  which  he  has  dealt  with  the  problems  and 
endeavoured  to  convey  his  experience  may  prove  of  some  value 
in  stimulating  others  to  take  a  deeper  interest  in  lubrication 
matters,  and  in  helping  them  to  get  a  clearer  view  of  possible 
problems  or  difficulties,  and  their  solution. 

Mechanical  and  electrical  engineers  in  charge  of  plant,  and 
lubricating  engineers  as  well  as  general  consulting  engineers  will, 
the  author  hopes  find  some  food  for  thought ;  they  may  not  always 
agree  with  the  theories  and  views  put  forward,  which  are  often 
novel  or  even  contrary  to  traditional  opinions;  but  in  that  case 
the  author  would  urge  them  to  try  out  his  recommendations, 
which  are  based  on  many  years  of  practical  experience  in  many 
parts  of  the  world;  they  will  then  be  able  to  draw  their  own 
conclusions,  and  constructive  criticism  will  always  be  welcomed 
by  the  author  and  gratefully  received. 

Engine  builders,  it  is  hoped,  will  find  information  which  will 
prove  useful  to  them  in  equipping  their  engines  and  machinery 
with  correctly  designed  lubricating  systems  and  appliances 


X  PREFACE 

and  in  giving  their  customers  sound  advice  or  instructions  with 
reference  to  the  grades  of  lubricants  required  and  the  best  manner 
of  using  them. 

Oil  chemists  and  manufacturers,  and  chemists  employed  by  oil 
consumers  will,  it  is  hoped,  find  the  book  helpful  in  pointing  out 
the  conditions  under  which  lubricants  have  to  work  for  particular 
types  of  machinery,  and  the  influences,  such  as  oxidation,  emulsi- 
fication,  etc.,  to  which  they  are  subjected  during  use.  The 
author  has  endeavored  to  focus  the  problems  and  describe  the 
mechanical  conditions  in  such  a  manner  as  to  assist  chemists  in 
deciding  which  are  the  physical  and  chemical  tests  of  greatest 
importance  in  each  particular  case. 

References  are  given  throughout  the  text  to  special  sources  of 
information,  but  the  author  wishes  particularly  to  record  his 
indebtedness  to  Mr.  L.  Archbutt  for  analyses  of  graphites;  to  Mr. 
J.  Hamilton  Gibson  for  photographs  of  stream  lines  in  connection 
with  MichelPs  thrust  blocks;  to  Mr.  I.  L.  Langton  for  information 
regarding  dielectric  strength  of  transformer  oils;  to  "The  Engi- 
neer" for  permission  to  make  use  of  some  articles  by  the  author 
on  ''Lubrication  of  modern  turbines;"  to  Mr.  E.  W.  Johnston 
for  information  regarding  the  use  of  Aquadag  in  steam  engines; 
to  the  Vacuum  Oil  Company  of  New  York  for  raising  no  objection 
to  the  author  making  use  of  several  technical  papers,  which  he 
prepared  during  the  time  he  was  associated  with  that  Company 
as  Chief  Engineer  in  London;  to  the  Controller  of  His  Majesty's 
Stationery  Office  for  permission  to  make  use  of  Bulletin  No.  2  on 
"  Cutting  Lubricants  and  Cooling  Liquids,"  and  Bulletin  No.  4 
on  "  Solid  Lubricants/'  both  of  which  have  been  published  by 
the  Department  of  Scientific  and  Industrial  Research,  and  the 
material  for  which  was  prepared  by  the  author;  and  to  Mr. 
W.  A.  E.  Woodman  for  valuable  assistance  in  preparing  many 
of  the  drawings. 

T.  C.  THOMSEN. 

LONDON,  ENG., 

August,  1920. 


CONTENTS 


PAGE 

PREFACE. v 

CHAPTER 

I.  MINERAL  LUBRICATING  OILS 1 

II.  FIXED  OILS  AND  FATS .    .• 15 

III.  SEMI-SOLID  LUBRICANTS 25 

IV.  SOLID  LUBRICANTS 29 

V.  TESTING  LUBRICANTS 33 

VI.  THE  LAWS  OF  FRICTION 79 

VII.  LUBRICATING  APPLIANCES 85 

VIII.  BEARINGS 99 

IX.  RING  OILING  BEARINGS  .    .    .    .' '        158 

X.  ELECTRIC  GENERATORS  AND  MOTORS 163 

XI.  PLAIN  THRUST  BEARINGS 166 

XII.  BALL  AND  ROLLER  BEARINGS 176 

XIII.  STEAM  TURBINES 192 

XIV.  BEARING  LUBRICATION  OF  STATIONARY  OPEIS  TYPE  STEAM 

ENGINES 238 

XV.  BEARING   LUBRICATION    OF    HIGH-SPEED    ENCLOSED    TYPE 

STEAM  ENGINES 243 

XVI.  CRANK  CHAMBER  EXPLOSIONS .         .    .  254 

XVII.  BEARING  LUBRICATION  OF  MARINE  STEAM  ENGINES   ....  257 

XVIII.  RAILWAY  ROLLING  STOCK 264 

XIX.  ELECTRIC  STREET  AND  RAIL  CARS 281 

XX.  TRANSMISSION  SHAFTING 286 

XXI.  MACHINE  TOOLS 290 

XXII.  TEXTIIE  MACHINERY 294 

XXIII.  MINE  CAR  LUBRICATION ! 320 

XXIV.  STEAM  ENGINES,  CYLINDERS  AND  VALVES    . 329 

XXV.  BLOWING  ENGINES  AND  AIR  COMPRESSORS 402 

XXVI.  REFRIGERATING  MACHINES 422 

XXVII.  GAS  ENGINES .  438 

XXVIII.   GASOLENE  ENGINES 472 

XXIX.  KEROSENE  OIL  ENGINE  AND  SEMI-DIESEL  ENGINES   ....  499 

XXX.  DIESEL  ENGINES • 514 

XXXI.  BRIEF  NOTES  ON  THE  LUBRICATION  OF  VARIOUS  WORKS  AND 

MACHINERY. 532 

'  XXXII.  OIL  RECOVERY  AND  PURIFICATION 550 

\    XXXIII.  OIL  STORAGE  AND  DISTRIBUTION 556 

1    XXXIV.  CUTTING  LUBRICANTS  AND  COOLANTS 559 

XXXV.  STATIC    ELECTRICAL    TRANSFORMERS     AND     OIL    FILLED 

SWITCHES .    .    .    .  577 

APPENDIX.    . 600 

INDEX 603 

xi 


THE 

PRACTICE  OF  LUBRICATION 

CHAPTER  I 

MINERAL  LUBRICATING  OILS 
PETROLEUM  CRUDE 

Oil  Wells. — Petroleum  crudes  are  secreted  by  nature  and  are 
found  in  many  countries  all  over  the  world. 

Occasionally,  petroleum  crude  is  found  lying  on  the  surface  of 
water  in  pools,  but  usually  it  is  found  at  various  depths  in  the 
earth,  from  a  few  hundred  feet  up  to  as  much  as  five  thousand 
feet.  To  bring  the  crude  to  the  surface  a  hole  is  drilled,  varying 
in  diameter  from  a  few  inches  up  to  18  inches  according  to  the 
depth. 

Wells  may  be  drilled  by  the  percussion  system  or  by  the  rotary 
system,  the  latter  being  mostly  used  for  drilling  through  soft 
ground.  By  the  percussion  system  a  chisel-shaped  heavy  steel 
"bit"  is  suspended  from  a  cable  or  a  long  chain  of  poles.  It  is 
lifted  and  dropped  alternately  by  means  of  a  steam  engine  situ- 
ated on  the  surface,  the  steel  bit  in  this  way  hammering  through 
the  earth  or  rock  and  deepening  the  bore  hole.  By  the  rotary 
system  the  drill  is  attached  to  the  lower  end  of  a  length  of  tubes 
and  is  rotated  by  a  steam  engine  or  electric  motor  situated  on 
the  surface.  In  order  to  remove  from  the  bore  hole  sand  and  frag- 
ments of  rock  a  stream  of  water  is  continuously  pumped  through 
this  long  tube,  and  on  rising  through  the  hole  it  carries  away  the 
sand  and  fragments. 

When  a  certain  depth  has  been  reached,  steel  piping  called 
"casing"  of  slightly  less  diameter  than  the  hole  (from  4  inches  to 
18  inches  in  diameter)  is  driven  into  the  ground.  The  hole  is 
then  continued  with  a  slightly  smaller  diameter  as  far  as  possible, 
when  again  a  smaller  diameter  "casing"  is  inserted,  so  that  the 
deeper  the  hole  the  smaller  is  the  diameter  at  the  bottom. 
Speaking  generally,  the  oil  should  be  reached  with  not  less  than 
a  four-inch  diameter  casing. 

It  is  usual  to  find  confined  with  the  oil  a  large  amount  of  gas 
under  great  pressure,  which  may  be  as  high  as  800  Ib.  per  square 
inch.  Due  to  this  pressure  the  oil  when  first  reached  is  forced 

1 


OF  LUBRICATION 


up  the  bore  hole  and  rises  many  feet  in  the  air;  such  a  well  is 
called  a  "  gusher.  " 

Some  gushers  have  produced  enormous  quantities  of  crude 
oil,  for  example  the  "Potrero  No.  4"  well  drilled  in  1910  by  the 
Mexican  Eagle  Oil  Company.  This  well  was  capable  of  giving 
about  120,000  barrels  of  crude  oil  daily  but  has  now  turned  into 
salt  water. 

Another  well,  "Dos  Bocas,  "  drilled  in  1908  by  the  same 
Company  was  probably  the  largest  oil  well  the  world  has  ever 
seen;  unfortunately  it  could  not  be  controlled,  and  drained  the 
field.  The  gas  and  oil  pressure  was  so  enormous  that  the  heavy 
casing,  2,000  feet  deep,  was  hurled  bodily  into  the  air.  This 
well  has  probably  been  the  most  spectacular  well  in  the  world. 
It  burned  for  40  days  with  a  flame  mounting  to  1,800  feet,  and 
newspapers  could  be  read  seven  miles  away  by  its  light.  After 
some  months  the  enormous  flow  of  oil  ceased,  the  original  eight- 
inch  hole  developed  into  a  huge  crater  many  acres  in  extent,  and 
a  daily  volume  of  several  million  of  barrels  of  salt  water  is  flowing 
from  it  at  the  present  day. 

When  the  gas  pressure  is  sufficiently  reduced  in  an  old  well, 
it  is  no  longer  a  "  flowing  well"  but  becomes  a  "pumping  well," 
and  the  output  is  reduced  to  a  small  fraction  of  its  former  value. 

Production  of  Petroleum  Crude.  —  Table  No.  1  shows  the 
world's  production  of  petroleum  crude  oil  in  metric  tons. 

The  United  States,  Russia  and  Mexico  are  the  three  great  oil- 
producing  countries. 

United  States.  —  The  production  is  still  increasing  in  the  United 
States,  but  will  probably  not  increase  much  longer;  many  of  the 
old  American  fields  (Pennsylvania,  etc.)  are  becoming  exhausted; 
the  new  fields  discovered  in  California  and  Oklahoma  have,  how- 
ever, made  up  for  the  decreased  production  in  the  older  fields. 

Russia.  —  There  are  still  large  possibilities  of  increased  pro- 
duction, but  the  development  of  the  oil  industry  is  handicapped 
by  the  political  conditions. 

Mexico.  —  The  Mexican  oil  industry  has  developed  rapidly 
since  1908.  The  potential  resources  are  enormous,  being  pro- 
bably as  great  as  or  even  greater  than  the  resources  of  the  United 
States. 

Origin  of  Petroleum  Crude.—  There  are  three  theories  held 
concerning  the  origin  of  crude  oils,  but  no  one  is  universally 
accepted. 

1.  Inorganic  Theory.  —  According  to  this  theory,  petroleum  is 
produced  deep  down  in  the  crust  of  the  earth  by  the  action  of 
high  temperature  and  pressure  on  the  minerals  found  there; 


MINERAL  LUBRICATING  OILS  3 

TABLE  1. — WORLD'S  PRODUCTION  OF  PETROLEUM  CRUDE  OIL  IN  METRIC 

TONS 


1915 

1916 

1917 

1918 

United  States  
Russia  
Mexico 

38,583,063 
9,385,000 
4,846,471 

37,864,031 
9,045,700 
6,742,480 

43,953,560 
8,980,790 
8,264,260 

47,715,580 
9,515,510 
5,500,000 

Roumania 

1,673,145 

1,432,296 

300,000 

1,260,000 

Galicia  

578,388 

878,670 

780,000 

786,000 

Dutch  East  Indies  .  .  . 
British  East  Indies  .  . 
Japan                       .  .  . 

1,710,000 
1,093,667 
415,785 

1,820,247 
1,097,143 
399,624 

1,700,000 
1,100,000 
400,000 

1,800,000 
1,060,000 
315,000 

Persia                 "" 

400,000 

600,000 

800,000 

900,000 

Peru           

331,633 

340,000 

340,000 

340,000 

Argentine 

91,000 

130,000 

207,000 

200,000 

United  Kingdom  .... 
Germany  
Egypt. 

300,000 
140,000 
33,600 

300,000 
130,000 
54,800 

300,000 
140,000 
134,500 

300,000 
140,000 
333,000 

Trinidad          

155,000 

160,000 

220,000 

291,100 

Canada. 

28,729 

26,416 

25,100 

40,000 

Italy  
Other    countries,  ap- 
proximately   

5,500 
40,000 

5,500 
40,000 

5,500 
40,000 

5,500 
40,000 

Total  

59,810,981 

61,066,907 

67,690,710 

68,541,690 

1  Metric  Ton  =  2,204  Ib.  =  1,000  kilograms. 

carbon  and  hydrogen  are  supposed  to  have  combined  and  formed 
the  hydrocafbons  which  are  the  chief  constituents  of  petroleum 
crude.  Only  a  minority  of  geologists  favor  this  theory. 

2.  Vegetation    Theory. — According    to    this  theory,  vegetable 
matter  has  been  covered  by  a  layer  of  impervious  material;  the 
air  thus  being  excluded,  rotting  was  prevented,  and  slow  decay 
during  hundreds  of  thousands  of  years  transformed  the  vegetable 
matter  into  petroleum  crude  oil  and  petroleum  gas.     Several 
geologists  favor  this  theory. 

3.  Marine  Animal  Theory. — According  to  this  theory,  dead 
fishes  or  tiny  marine  animals  with  chalk  shells  were  covered  over 
by  a  layer  of  impervious  material  and  gradually  transformed 
into  crude  oil  and  gas.     Most  geologists  favor  this  theory. 

Whichever  theory  is  correct,  it  seems  certain  that  the  world's 
stocks  of  petroleum  crude  are  practically  complete  and  are  being 
rapidly  consumed. 

Composition  and  Character  of  Petroleum  Crude. — When  the 
crude  comes  to  the  surface  it  often  contains  water  (frequently 
salt  water)  and  dirt,  which  are  separated  out  in  large  collecting 
and  settling  reservoirs. 


4  PRACTICE  OF  LUBRICATION 

The  crude  is  rarely  transparent;  the  color  is  usually  dark 
brown  or  black. 

Petroleum  crude  consists  chiefly  of  carbon  (C)  and  hydrogen 
(H)  in  the  form  of  hydrocarbons.  Besides  carbon  and  hydrogen, 
there  is  usually  also  a  certain  amount  of  oxygen,  nitrogen  and 
sulphur  present. 

The  percentages  of  the  various  chemical  constituents  vary 
within  limits  as  indicated  in  the  following  table : 

Carbon 81.00    to  88.0  per  cent. 

Hydrogen 10 . 00    to  14 . 0  per  cent. 

Oxygen 0.01    to    1.2  per  cent. 

Nitrogen 0 . 002  to    1.7  per  cent. 

Sulphur 0 . 01    to    5 . 0  per  cent. 

Hydrocarbons: 

Paraffins  (Cn.H2n  +  2). — The  molecules  of  these  hydrocarbons 
are  bound  together  in  the  form  of  chains,  and  are  members  of 
the  large  family  of  hydrocarbons  known  as  open-chain  hydro- 
carbons, thus: 

H    H  H    H  H    H 

H— C— C C— C C— C— H 

II  II  II 

H    H  H    H  H    H 

As  all  the  carbon  atoms  are  fully  engaged,  each  carbon  atom 
being  tetravalent  and  attached  to  four  other  atoms,  the  paraffins 
are  called  saturated  hydrocarbons. 

Olefines  (Cn.H2n). — The  olefines  are  also  open-chain  hydro- 
carbons, but  their  molecules  have  two  atoms  of  hydrogen  less 
than  the  paraffins,  thus: 

HH  HHHH  HH 

H-C-C C-C  =  C-C C— C— H 

II  I  I  II 

H    H  H  H  H    H 

They  are  called  unsaturated,  because  they  are  capable  of  absorb- 
ing hydrogen,  oxygen,  sulphur,  etc.,  to  a  value  equivalent  to  two 
atoms  of  hydrogen  per  molecule. 

Napthenes  (Cn.H2n). — Naphthenes  are  closed-chain  hydro- 
carbons; they  have  the  same  chemical  formula  as  the  olefines, 
but  the  atoms  are  not  arranged  in  the  form  of  open  chains,  but 
more  in  the  nature  of  rings  or  closed  chains,  in  such  a  manner  as 
to  fully  saturate  all  the  carbon  atoms. 

Naphthenes  being  saturated  hydrocarbons  are  consequently 
more  stable  than  the  olefines. 


MINERAL  LUBRICATING  OILS  5 

CnH2n  —  2,  CnH2n—4,  etc.  Most  hydrocarbons  of  the  formutce 
CnH2n  — 2,  CnH2n— 4,  etc.,  are  more  or  less  unsaturated,  and 
the  more  so  the  less  hydrogen  they  contain. 

Hydrocarbons  having  from  1  to  about  15  carbon  atoms  per 
molecule  represent  the  light  products  of  petroleum  crude,  viz. 
petroleum  gas,  gasolenes,  kerosenes,  and  light  transformer  and 
spindle  oils. 

Most  lubricating  oils  are  mixtures  of  hydrocarbons  possessing 
more  than  15  carbon  atoms  per  molecule;  the  greater  the  number 
of  carbon  atoms,  -the  greater  is  the  viscosity  of  the  oil.  Comparing 
two  hydrocarbons  having  the  same  number  of  carbon  atoms,  the 
one  containing  the  least  hydrogen  is  the  more  viscous  of  the  two, 
but  its  viscosity  is  less  stable,  i.e.,  it  changes  more  rapidly  with 
changes  in  temperature. 

Most  petroleum  crudes  are  very  complicated  in  character,  and 
it  is  difficult  to  classify  them;  they  contain  hydrocarbons  of 
practically  all  types,  but  the  proportions  vary  considerably  ac- 
cording to  the  origin  of  the  petroleum. 

Petroleum  crudes  are,  however,  referred  to  as  Paraffin  Base 
Crudes,  Asphaltic  Base  Crudes,  Russian  Crudes,  and  Mixed 
Base  Crudes. 

Paraffin  base  crudes  are  so  called  because  they  contain 
paraffin  hydrocarbons  (CnH2n+2).  There  are  only  a  few  lubri- 
cating oils  of  low  viscosity  which  are  actually  paraffin  hydro- 
carbons, as  paraffins  from  CnH36  and  upward  represent  the 
hydrocarbons  present  in  paraffin  waxes.  The  heavy  viscosity 
lubricating  oils  which  are  found  in  paraffin  base  crudes  are  largely 
composed  of  olefines  and  naphthenes  (CnH2n)  and  acetylenes 
(CnH2n  —  2) .  As  paraffin  base  crudes  always  contain  a  certain 
amount  of  paraffin  wax,  usually  about  2  per  cent,  lubricating 
oils  made  from  such  crudes  have  high  setting  points. 

The  most  important  supplies  of  paraffin  base  crudes  come  from 
Pennsylvania  and  Ohio  in  the  United  States.  They  are  fairly 
fluid,  rich  in  gasolenes  and  kerosenes,  usually  contain  only  a 
little  asphalt,  sulphur,  oxygen  or  nitrogen,  and  have  a  low  spe- 
cific gravity. 

Asphaltic  base  crudes  are  so  called  because  they  contain  a 
large  amount  of  asphalt;  they  usually  contain  certain  small  per- 
centages of  sulphur,  oxygen  and  nitrogen.  The  crudes  from 
California,  Mexico,  Texas,  and  South  America  belong  to  this 
class. 

They  are  very  viscous,  black  in  color,  rich  in  lubricating  oils, 
fuel  oils  and  asphalt,  and  have  a  high  specific  gravity;  they  often 
contain  complex  sulphur  compounds,  which  are  difficult  to  extract. 


6  PRACTICE  OF  LUBRICATION 

The  lubricating  oils  produced  from  non-paraffinic  asphaltic 
base  crudes  have  low  setting  points  and  possess  a  wide  range  of 
viscosity,  ranging  from  quite  thin  oils  to  exceedingly  viscous 
oils. 

The  hydrocarbons  in  asphaltic  base  crudes  are  lower  in  hydro- 
gen than  the  paraffins,  although  paraffins  are  often  present, 
particularly  in  some  Mexican  crudes.  For  example,  California 
crudes  contain  olefines  (CnH2n),  asphaltic  hydrocarbons  (Cn- 
H2n-4)  and  also  some  benzenes  (CnH2— 6).  Texas  crudes  are 
rich  in  asphaltic  hydrocarbons. 

Russian  crudes  are  in  a  class  by  themselves,  consisting  chiefly 
of  naphthenes  (CnH2n) ;  they  also  contain  a  small  percentage  of 
acetylene  hydrocarbons  (CnH2n  — 2). 

Russian  crudes  contain  little  or  no  paraffin  wax;  hence  produce 
lubricating  oils  with  low  setting  points. 

Mixed  base  crudes  are  crudes  of  a  character  intermediary 
between  paraffin  base  crudes  and  asphaltic  base  crudes,  contain- 
ing both  paraffin  wax  and  asphalt. 

DISTILLATION  AND  REFINING 

Petroleum  crude'is  a  mixture  of  many  hydrocarbons,  all  having 
different  boiling  points. 

The  crude  is  gradually  heated  in  cylindrical  stills  and  the 
hydrocarbons  distil  over  as  their  boiling  points  are  reached;  the 
vapors  escape  through  a  dome  at  the  top  of  the  still,  pass  a  coil 
of  pipes  immersed  in  cold  water,  become  liquefied  and  run  through 
an  inspection  box  with  glass  windows  in  the  "tail"  house,  whence 
the  various  "fractions"  are  directed  into  their  respective  collect- 
ing tanks.  The  specific  gravity  and  color  form  a  sufficient 
guide  for  the  attendant  to  enable  him  to  judge  when  to  "cut" 
the  various  fractions. 

The  distillation  may  be  carried  out  hy  the  intermittent  system 
or  the  continuous  system. 

By  the  Intermittent  System  batches  of  oil  are  treated  in  separate 
cylindrical  stills,  the  crude  stills  being  as  much  as  45  feet  long 
and  12  feet  in  diameter,  holding  about  1000  barrels  of  crude. 
The  distillation  may  be  carried  to  a  finish  in  the  crude  stills,  as  in 
the  Tower  vertical  still,  or  the  crude  may  only  be  freed  from  the 
lighter  fractions  (gasolenes  and  kerosenes),  and  the  residue, 
known  as  tar,  transferred  to  other  stills  (tar  stills),  holding  about 
250  barrels  each,  in  which'the  final  distillation  takes  place. 

By  the  Continuous  System  the  crude  oil  passes  slowly  but  con- 
tinuously through  a  row  of  stills,  perhaps  ten  in  number,  all 
connected  together.  The  stills  are  placed  at  lower  and  lower 


MINERAL  LUBRICATING  OILS  7 

levels,  so  that  the  crude  flows  by  gravity  from  the  first  to  the 
last  still,  passing  through  all  the  stills  one  after  the  other.  Each 
still  is  heated  to  a  higher  temperature  than  the  previous  one,  so 
that  a  definite  distillate  is  being  taken  out  from  each  still,  and 
the  character  of  the  distillates  can  be  varied  at  will  by  regulating 
the  temperatures  of  the  various  stills  and  the  rapidity  of  the  flow 
of  crude.  This  system  is  largely  used  in  Russia  and  is  rapidly 
gaining  favor  in  America  and  Mexico. 

Cracking. — The  crude  itself  or  certain  distillates  are  cracked 
when  it  is  desired  to  produce  a  maximum  amount  of  light  frac- 
tions. When  hydrocarbons  are  suddenly  heated  to  a  tempera- 
ture above  their  boiling  points  and  not  given  time  to  distil  in  the 
ordinary  way,  they  decompose  into  simpler  hydrocarbons  which 
possess  lower  boiling  points;  this  process  is  called  " cracking." 

When  crude  oil  (after  gasolenes  and  kerosenes  have  been  re- 
moved) is  slowly  heated  for  a  prolonged  period,  the  oil  falls 
back  from  the  cooled  top  of  the  stills  into  the  hot  liquid,  and  in 
this  way  a  large  portion  of  kerosene  is  produced  from  the  heavier 
fractions  of  the  crude.  This  process  is,  .however,  slow,  and  ex- 
perience has  shown  that  quicker  and  more  effective  results  can  be 
obtained  in  special  cracking  stills,  heated  to  a  high  temperature, 
into  which  the  kerosene,  gas  oil,  or  other  heavy  oil  is  sprayed. 
The  effect  of  cracking  on  the  lubricating  oils  is  that  viscous 
oils  are  decomposed  into  low-viscosity  oils.  In  certain  cracking 
processes  the  oil  is  cracked  under  a  pressure  of  several  atmos- 
pheres, which  further  increases  the  yield  of  lower  boiling  point 
fractions.  These  improved  cracking  stills  are  responsible  for 
the  large  increase  in  production  of  cracked  motor  spirits  and 
kerosenes'which  has  taken  place  during  recent  years  to  meet  the 
increased  demand  for  motor  spirits. 

With  every  cracking  process  a  certain  amount  of  unsaturated 
hydrocarbons  is  formed,  but  most  of  the  undesirable  ones  may 
be  removed  by  treatment  with  sulphuric  acid  or  by  filtration 
through  Fuller's  earth  or  like  material. 

Steam  Distillation. — When  it  is  desired  to  produce  a  maximum 
amount  of  lubricating  oils  and  to  minimize  cracking,  the  stills  in 
addition  to  being  heated  by  fire  externally  are  heated  internally 
by  live  superheated  steam,  introduced  directly  into  the  body 
of  the  oil  near  the  bottom  of  the  stills,  so  as  to  mix  well  with  the 
oil  and  also  to  prevent  overheating  of  the  still  bottom.  To 
increase  further  the  yield  of  lubricating  oils  and  to  prevent  over- 
heating, the  oils  may  be  distilled  under  a  partial  vacuum,  as  the 
vacuum  causes  the  various  fractions  to  distil  over  at  lower 
temperatures. 


8  PRACTICE  OF  LUBRICATION 

When  the  distillation  is  assisted  by  the  application  of  steam 
with  or  without  vacuum,  a  lower  percentage  of  unsaturated 
hydrocarbons  is  formed  than  when  distilling  without  steam,  and 
less  acid  or  treatment  is  therefore  required  when  refining  the 
distillates. 

Redistillation. — Usually  the  crude  is  split  into  only  a  few 
fractions,  which  may  be  further  separated  into  a  greater 
number  of  fractions  by  redistillation.  For  example,  crude 
gasolene  is  redistilled  by  steam  distillation  into  light  and 
heavy  gasolene,  and  the  residue  may  be  used  as  first-grade 
turpentine  substitute  or  kerosene  stock.  Crude  kerosene  is 
similarly  redistilled  into  the  particular  grades  of  kerosene 
desired,  and  if  the  crude  kerosene  contains  too  light  fractions, 
these  may  be  utilized  as  a  second-grade  turpentine  substitute, 
whereas  too  heavy  fractions  are  mixed  with  the  gas  oil  distillates. 
Lubricating  oil  distillates  are  also  redistilled,  by  fire  and  live 
steam  distillation  with  or  without  vacuum,  and  separated  into 
•  heavier  and  lighter  lubricating  oils. 

PETROLEUM  PRODUCTS 

When  the  light  fractions,  viz.  gasolenes  (distilling  over  up 
to  150°C.)  and  kerosenes  (distilling  over  between  150°C.  and 
300°C.)  have  been  distilled  off,  the  next  distillate  is  a  high  flash 
burning  oil  called  300  fire  test  oil,  mineral  colza,  mineral  sperm, 
or  mineral  seal;  but  if  the  quality  of  this  distillate  is  not  such  as 
to  produce  a  satisfactory  burning  oil,  the  distillate  is  called  solar 
oil  or  gas  oil,  and  is  used  for  making  oil  gas  or  carburetted  water 
gas,  or  as  a  high  class  fuel  oil  for  semi-Diesel  or  Diesel  oil  engines. 
Also,  when  mixed  with  heavy  black  residual  oils  (asphaltic  or 
non-asphaltic)  it  is  used  as  fuel  oil  in  Diesel  engines,  or  in  fur- 
naces using  liquid  fuel. 

The  lubricating  oil  fraction  or  fractions  (from  which  spindle 
oils,  engine  and  machinery  oils  are  manufactured)  now  distil 
over  and  if  the  crude  contains  wax  the  distillate  containing  wax 
is  chilled  to  about  20-25°F.,  and  in  the  wax  filter  press  the  oils 
are  squeezed  out  and  the  wax  left  in  the  press.  Lubricating  oils 
made  from  a  paraffin  base  crude,  therefore,  have  setting  points 
of  about  20-25°F.  unless  they  are  specially  treated  to  remove 
more  of  the  wax;  they  may  also  be  blended  with  other  oils  having 
very  low  setting  points  so  as  to  produce  oils  with  low  setting 
points. 

The  wax  when  removed  from  the  press  contains  as  much  as 
50  per  cent,  of  oil  which  is  removed  by  ''sweating,"  viz.  slow 


MINERAL  LUBRICATING  OILS  9 

prolonged  heating  of  the  wax.  The  melting  points  of  the  sweated 
wax  range  from  100°F.  to  130°F.;  it  is  melted,  crystallized  in 
molds,  and  sold  as  white  paraffin  wax  used  chiefly  for  making 
candles,  also  for  preserving  fruit  and  jellies,  for  polishing 
floors,  etc. 

The  pressed  lubricating  oils  are  redistilled  into  heavier  and 
lighter  oils  and  either  treated  by  sulphuric  acid  or  filtered  through 
Fuller's  earth  or  bone  black  (animal  charcoal)  in  order  to  remove 
unstable  hydrocarbons  or  other  undesirable  elements,  and  to 
lighten  the  color. 

Sunbieaching,  exposing  the  oil  in  shallow  troughs,  has  the 
effect  of  forming  a  heavy  sludge  of  the  unstable  elements,  which 
sinks  to  the  bottom  and  the  oil  becomes  lighter  in  color.  After 
exposure  for  some  time  the  oil  commences  to  darken,  and  the 
sunbleaching  process  should  then  be  stopped,  as  otherwise  the 
oil  is  injured. 

After  the  oil  has  been  treated  with  acid  in  vertical,  lead-lined 
agitators  it  is  washed  with  water,  neutralized  with  an  alkali, 
washed  again  with  water  to  remove  the  alkali,  and  finally  blown 
with  hot  air  to  remove  the  last  traces  of  moisture;  it  should  then 
be  bright  and  transparent,  and  be  free  from  acid  or  alkali. 

When  filtered  through  Fuller's  earth  or  animal  charcoal  the 
first  few  gallons  of  oil  which  come  out  are  colorless,  but  as  the 
filtering  material  becomes  saturated  with  the  absorbed  impurities 
and  coloring  matter  the  color  of  the  oil  gradually  darkens. 
Each  grade  of  oil  is  filtered  to  be  within  the  standard  color  limits 
for  that  particular  grade, 

Dark  Cylinder  Stock. — When  the  distillates  containing  the 
light  and  heavy  lubricating  oils  have  passed  off  there  remains  in 
the  still  a  very  heavy  viscous  dark  oil  used  principally  for  internal 
lubrication  of  steam  engine  cylinders  and  valves.  If  it  contains 
too  much  asphalt  it  cannot  be  used  as  a  cylinder  oil,  but  may  be 
mixed  with  light  viscosity  lubricating  oils  to  produce  dark  lu- 
bricating oils. 

Filtered  cylinder  stock  is  produced  from  dark  cylinder  stock 
by  filtration;  the  color  becomes  green,  amber;  the  heavy  gravity 
tarry  matter  is  removed,  the  viscosity  is  reduced  15  per  cent, 
to  25  per  cent,  and  the  specific  gravity  is  likewise  reduced,  but  the 
setting  point  is  increased. 

Petroleum  jelly  (mineral  jelly,  petrolatum)  is  an  amorphous 
wax  produced  by  slow  cooling  of  dark  cylinder  stock  diluted  with 
gasolene;  the  petroleum  jelly  separates  out  and  is  afterwards  re- 
fined (decolorized)  by  hot  filtration.  Petroleum  jelly  is  used 
in  the  manufacture  of  cordite  (an  addition  of  2  per  cent,  of  jelly 


10  PRACTICE  OF  LUBRICATION 

makes  the  cordite  less  brittle),  as  an  anti-rust  grease,  for  oint- 
ments (veterinary  purposes),  etc.,  etc.  Vaseline  is  the  proprie- 
tary name  given  to  a  certain  high  grade  petroleum  jelly. 

Cold  Test  Cylinder  Stock. — By  distilling  off  the  gasolene  from 
the  liquid  portion  a  low  cold  test  cylinder  stock  is  produced,  which 
may  be  further  refined  by  filtration.  Cylinder  stocks  are  almost 
exclusively  produced  from  paraffin  base  crudes.  When  a  paraffin 
base  crude  is  cracked  during  distillation  and  it  is  not  desired  to 
produce  cylinder  stock,  the  cracking  of  the  heavy  distillates  pro- 
duces carbon,  so  that  as  much  as  5  per  cent,  of  the  crude  may 
remain  in  the  still  in  the  form  of  petroleum  coke,  which  is  used  for 
smelting  furnaces,  for  electric  arc  carbons,  or  as  refinery  fuel, 
according  to  its  quality. 

When  asphaltic  base  crudes  are  distilled,  cylinder  stock  can 
rarely  be  produced;  the  residue  consists  of  asphaltic  matter. 
Heavy  liquid  asphaltic  residues  are  used  as  road  spraying  ma- 
terial in  place  of  coal  tar,  and  are  also  used  in  the  manufacture 
of  various  liquid  fuels. 

Petroleum  pitch  or  bitumen  has  found  a  most  important  use, 
chiefly  in  the  making  of  wearing  surfaces  for  modern  roads;  also 
for  roofing  felts,  bituminous  paints,  etc.  It  is  also  used  in  the 
making  of  hot  neck  greases  for  steel  works  rolling  mills. 

When  the  liquid  bitumen  in  the  stills  is  " blown"  with  air,  it 
oxidizes  into  blown  asphalt,  which  has  a  rubbery  nature  and  finds 
an  important  use  as  rubber  substitute,  for  roofing  felt,  etc. 

SHALE  OIL 

Oil  shale  is  a  dark  grey  or  black  mineral  yielding  about  23 
gallons  of  crude  shale  oil  per  ton  of  shale.  By  distillation  is 
produced  crude  naphtha,  green  oil,  and  coke.  The  crude  naph- 
tha is  redistilled  and  yields  mainly  motor  spirit.  The  green  oil 
yields  paraffin  wax,  kerosene,  fuel  oil,  gas  oil,  and  lubricating 
oils. 

The  lubricating  oils  are  of  very  low  vicosity  and  are  chiefly 
used  as  batching  oils  (for  softening  the  fibres  of  flax,  jute,  etc., 
during  their  process  of  manufacture  into  yarns) ;  they  contain  a 
large  percentage  of  unsaturated  hydrocarbons  (defines).  The 
setting  point  is  about  32°F.  When  used  as  lubricants  they  are 
rarely  used  alone  but  are  usually  mixed  with  5  per  cent,  to  15 
per  cent,  of  fixed  oil  (sperm,  whale  or  lard)  to  increase  their 
oiliness;  they  can  then  be  used  for  lubricating  light,  quick 
running  spindles  and  machinery,  but  are  inclined  to  gum  on 
account  of  the  presence  of  highly  unsaturated  hydrocarbons. 


MINERAL  LUBRICATING  OILS  11 

CLASSIFICATION  OF  LUBRICATING  OILS 

Dark  Cylinder  Oils. — Dark  cylinder  oils  are  the  undistilled 
dark  residues  left  in  the  stills  (by  steam  distillation  chiefly  of 
non-asphaltic  crude),  freed  from  solid  impurities  but  not  filtered. 
They  are  chiefly  used  for  lubrication  of  steam  engine  cylinders 
and  valves,  either  alone  or  mixed  with  from  3  per  cent,  to  10  per 
cent,  of  acidless  tallow  oil.  The  ordinary  characteristics  are  as 
follows: 

Flash  point  open From  500°F.  to  620°F. 

Specific  gravity From  0.900  to  0.916 

Saybolt  viscosity  at  212°F 135  sec.  to  250  sec. 

Color,  in  reflected  light Dark  brown  or  dark  green  to  black 

Color  in  transmittent  light Dark  brown  to  black 

Setting  point 35°F.  to  60°F. 

Filtered  Cylinder  Oils. — Filtered  cylinder  oils  are  made  from 
dark  cylinder  oils  by  filtration.  They  represent  the  highest 
quality  oils  used  for  internal  lubrication  of  steam  engines;  they 
are  used  either  alone  or  mixed  with  from  3  per  cent,  to  12  per 
cent,  of  acidless  tallow  oil.  They  are  also  largely  used  for  mixing 
with  lower  viscosity  oils  to  produce  heavy  viscosity  oils  for  inter- 
nal combustion  engines,  or  heavy  viscosity  engine  and  machinery 
oils,  air  compressor  oils,  circulation  oils,  etc. 

Flash  point  open From  490°F.  to  580°F. 

Specific  gravity From  0.875  to  0.895 

Saybolt  viscosity  at  212°F 100  sec.  to  160  sec. 

Color,  in  reflected  light Green,  amber 

Color  in  transmittent  light >  .  .  .    Deep  red 

Setting  point 40°F.  to  80°F. 

Red  Oils. — Red  oils  are  fire-distilled  (with  or  without  steam) 
acid  treated  oils.  They  represent  a  large  portion  of  the  medium 
and  heavy  viscosity  oils  used  for  general  lubrication  of  engines, 
shafting  and  machinery  of  all  kinds.  Mixed  with  filtered 
cylinder  oil,  red  oils  produce  very  heavy  viscosity  engine  and 
machinery  oils. 

They  must  not  be  used  for  circulation  service  as  in  steam  tur- 
bines, because  they  do  not  separate  well  from  water,  causing 
emulsification  and  objectionable  deposits. 

Red  oils,  made  from  paraffin  base  crude,  are  not  very  satis- 
factory for  making  oils  for  internal  combustion  engines,  as  they 
produce  a  great  deal  of  hard  and  brittle  carbon.  When  made 
from  asphaltic  base  crudes,  they  produce  less  carbon  deposit 
and  it  is  of  a  soft  crumbly  nature. 

The  heavy  red  oils,  when  mixed  with  from  5  per  cent,  to 


12  PRACTICE  OF  LUBRICATION 

20  per  cent,  of  fixed  oil  (blown  or  unblown)  produce  some  of  the 
lighter  viscosity  marine  and  railway  engine  oils. 

Flash  point  open 380°F.  to  440°F. 

Specific  gravity 0.900  to  0.915 

Saybolt  viscosity  at  70°F. 600  sec.  to  1,500  sec. 

Color Red 

Setting  point  (paraffin  base) 20°F.  to  30°F. 

Setting  point  (asphaltic  base) 0°F.  to  20°F. 

Pale  Oils. — Pale  oils  are  fire  distilled  (with  or  without  steam), 
heavily  acid  treated  or  heavily  filtered  oils.  They  are  of  light  to 
medium  viscosity,  and  are  used  for  lubricating  quick-running 
machinery,  such  as  high  speed  shafting,  electric  motors,  textile 
machinery,  also  for  manufacturing  yellow  lubricating  greases. 
Further,  they  are  used  largely  for  lubricating  small  and  medium 
size  internal  combustion  engines  of  all  kinds,  either  alone  or 
mixed  with  from  3  per  cent,  to  10  per  cent,  of  fixed  oil,  or  filtered 
cylinder  oil  (when  a  heavy  viscosity  oil  is  required). 

Pale  oils  produce  less  carbon  deposit  than  red  oils  when  used 
for  lubricating  internal  combustion  engines. 

Flash  point  open 275°F.  to  420°F. 

Specific  gravity 0.870  to  0.910 

Saybolt  viscosity  at  70°F 60  sec.  to  850  sec. 

Color Pale 

Setting  point  (paraffin  base) 15°F.  to  25°F. 

Setting  point  (asphaltic  base) 0°F.  to  15°F. 

Neutral  Oils. — Neutral  oils  are  steam  or  fire  distilled  oils  (freed 
from  paraffin  wax,  if  wax  is  present),  sunbleached  and  filtered 
through  Fuller's  earth  and  when  not  acid  treated  are  called 
filtered  neutral  oils.  Most  neutral  oils  are  filtered  rather  than 
acid  treated. 

Neutral  oils  are  of  light  or  medium  viscosity  and  used  for 
similar  purposes  as  pale  oils;  neutral  filtered  oils  are  more  suitable 
than  pale  oils  for  self  oiling  bearings,  where  the  oil  is  used  over 
and  over  again.  Neutral  filtered  oils  are  largely  used  as  circu- 
lation oils  (for  enclosed  type  steam  engines  and  steam  turbines) 
either  alone  or  mixed  with  filtered  cylinder  oil,  as  they  separate 
well  from  water. 

By  redistillation,  or  "reducing, "  the  neutral  oils  are  separated 
into  (a)  viscous  and  (b)  non-viscous  neutral  oils. 
(a)   Viscous  Neutral  Oils. 

Flash  point  open 350°F.  to  400°F. 

Specific  gravity 0.850  to  0.900 

Saybolt  viscosity  at  70°F 180  to  500  sec. 

Color Pale  to  light  rod 

Setting  point  (paraffin  base) 15°F.  to  25°F. 

Setting  point  (asphaltic  base) 0°F.  to  1£°F. 


MINERAL  LUBRICATING  OILS  13 

(6)  Non-viscous  Neutral  Oils. 

Flash  point  open 320°F.  to  360°F. 

Specific  gravity. 0.840  to  0.890 

Saybolt  viscosity  at  70°F 70  to  180  sec. 

Color Pale 

Setting  point  (paraffin  base) 15°F.  to  25°F. 

Setting  point  (asphaltic  base) 0°F.  to  15°F. 

Dark  Lubricating  Oils. — Dark  lubricating  oils  are  such  un- 
distilled  residues  from  the  crude  or  from  the  redistillation  of 
lubricating  oil  distillates  which,  because  of  too  low  a  viscosity 
or  for  other  reasons,  are  considered  unsuitable  as  cylinder  oils. 
Dark  lubricating  oils  are  usually  mixtures  of  such  residues  with 
low  viscosity  lubricating  oils  to  produce  the  required  viscosity. 

Dark  lubricating  oils  are  used  for  rough  machinery  in  collieries 
and  steel  works,  as  cheap  oils  for  lubricating  the  axles  of  rail- 
way carriages  and  for  making  black  lubricating  greases,  for 
rough  service. 

Flash  point  open 300°F.  to  450°F. 

Specific  gravity 0.890  to  0.950 

Saybolt  viscosity  at  140°F 200  sec.  to  350  sec. 

Color Dark  green  or  brown  to  black 

Setting  point 10°F.  to  60°F. 

Asphalt Less  than  5  per  cent. 

Viscous  Low  Setting  Point  Oils. — These  oils  are  fire  distilled 
and  made  from  non-paraffinic  base  crude,  acid  treated  and  fil- 
tered. They  are  chiefly  used  in  the  manufacture  of  heavy  vis- 
cosity railway  and  marine  engine  oils,  compounded  with  from 
10  per  cent,  to  25  per  cent,  of  fixed  oil  (blown  or  unblown);  they 
are  also  largely  used  in  the  manufacture  of  heavy  viscosity  oils 
for  internal  combustion  engines,  as  they  produce  only  a  little 
carbon  deposit,  and  the  carbon  is  soft.  As  motor  car  oils  they 
give  easy  starting  from  cold  on  account  of  their  low  setting 
points. 

Flash  point  open 385°F.  to  415°F. 

Specific  gravity 0.910  to  0.950 

Saybolt  viscosity  at  70°F 1200  to  4000  sec. 

Color Pale  to  red 

Setting  point Zero  F.  to  20°F. 

Non-viscous  Low  Setting  Point  Oils. — These  oils  are  either 
fire  distilled  or  steam  distilled,  acid  treated  or  acid  treated  and 
filtered;  they  may  possess  a  naturally  low  setting  point  (when 
made  from  a  non-paraffinic  base  crude)  or  they  are  cold  pressed 
at  zero  or  an  even  lower  temperature  to  extract  the  wax  and  to 
give  the  desired  low  setting  point. 

Non-viscous  low  setting  point  oils  are  chiefly  used  in  the  manu- 


14  PRACTICE  OF  LUBRICATION 

facture  of  oils  for  refrigerator  compressors  on  account  of  their 
low  setting  points;  very  low  setting  point  oils  are  used  for  lubri- 
cating certain  parts  of  high-flying  aeroplanes. 

Flash  point  open 280°F.  to  380°F. 

Specific  gravity 0.850  to  0.900 

Saybolt  viscosity  at  70°F 80  to  360  sec. 

Color Pale  or  red 

Setting  point -40°F.  to  zero  F. 

Bloomless  Oils.— Bloomless  oils  are  neutral  oils  which  have 
been  highly  filtered  and  may  also  have  been  sunbleached ;  they 
are  very  light  in  color  and  of  light  viscosity. 

To  remove  the  bloom  entirely  they  must  be  treated  with  nitro- 
naphthalene  or  other  chemicals. 

Bloomless  oils  are  used  for  adulterating  edible  oils;  also  in  the 
manufacture  of  stainless  loom  and  spindle  oils. 

White  Oils. — White  oils  are  pale  spindle  oils  which  have  been 
treated  with  fuming  sulphuric  acid  or  liquid  sulphur  dioxide, 
Fuller's  earth  filtration,  etc.;  in  order  to  remove  the  color 
completely.  They  are  easily  made  from  Russian  crudes  and 
are  largely  used  as  non-sludging  transformer  oils.  It  is  very 
difficult  to  remove  color  entirely  from  oils  produced  from 
paraffin  base  crudes. 

Medicinal  White  Oils. — Medicinal  white  oils  are  white  oils 
which  have  been  so  treated  as  to  remove  not  only  color  but 
also  all  taste  and  odor. 


CHAPTER  II 
FIXED  OILS  AND  FATS 


Vegetable  oils 
and  fats 

Vegetable  oils 
and  fats 

Animal  oils 
and  fats 

Animal  oils 
and  fats 

Castor  oil 

Olive  oil 

Tallow 

Dolphin  jaw  oil 

Rape  oil 

Cocoanut  oil 

Tallow  oil 

Melon  oil 

Blown  rape  oil 

Palm  oil 

Lard  oil 

Menhaden  oil 

Cottonseed  oil 

Palm  kernel  oil 

Neatsfoot  oil 

Cod  oil  and  other 

Blown      cotton- 

Peanut oil 

Sperm  oil 

fish  oils 

seed  oil 

Mustard  seed  oil 

Whale  oil 

Wool  grease 

Linseed  oil 

Rosin  oil 

Porpoise  jaw  oil 

Animal  and  vegetable  oils  are  called  " fixed"  oils  because  they 
cannot  like  mineral  oils  be  distilled  without  decomposition.  They 
also  differ  from  mineral  oils  in  that  they  contain  from  9.4  per 
cent,  to  12.5  per  cent,  oxygen. 

The  distinction  between  fixed  oils  and  fats  is  only  a  matter  of 
temperature;  all  fixed  oils  become  fats  at  or  above  0°F.  and  all 
fats  become  oils  at  or  below  125°F. 

Animal  oils  are  obtained  by  heating  the  fatty  tissues  of  animals, 
i.e.,  by  " rendering"  the  fat  or  by  boiling  out  the  fatty  oil  with 
water.  Vegetable  oils  occur  mostly  in  the  seeds  or  fruits  of 
plants  or  trees  and  are  obtained  either  by  pressing  or  by  chemical 
extraction  with  solvents.  Animal  oils  are  usually  either  colorless 
or  yellow.  Vegetable  oils  are  colorless,  yellow,  or  slightly  green 
(chlorophyll  present). 

All  fixed  oils  are  devoid  of  bloom  except  rosin  oil,  and  each 
variety  generally  has  a  distinctive  odor,  by  which  it  can  be  identi- 
fied. Their  specific  gravities  range  from  0.860  to  0.970.  Rosin 
oil  is  an  exception;  its  specific  gravity  may  be  as  high  as  1.0. 
Sperm  oil  has  the  lowest  viscosity  of  all  fixed  oils  and  castor  oil 
the  highest,  but  each  kind  of  oil  has  its  own  peculiar  viscosity, 
which  varies  only  slightly. 

All  fixed  oils  have  a  tendency  to  combine  with  oxygen,  and  as 
a  result  are  sooner  or  later  converted  into  solid  elastic  varnishes. 
As  a  result  of  this  tendency,  cotton  waste,  when  saturated  with 
fixed  oils  or  lubricating  oils  very  rich  in  fixed  oils,  has  been  known 

15 


16 


PRACTICE  OF  LUBRICATION 


occasionally  to  heat  gradually  and  finally  to  burst  into  flame. 
Dirty  cotton  waste,  which  contains  fixed  oil  must  therefore  be 
kept  in  receptacles  with  closed  lids. 

When  the  tendency  to  absorb  oxygen  is  marked,  the  fixed 
oils  are  called  drying  oils,  as  for  example,  linseed  oil.  When  the 
tendency  is  moderate  or  only  slight,  the  oils  are  called  semi-drying 
or  non-drying  oils  respectively,  and  it  is  only  from  these  two  types 
of  fixed  oils  that  lubricants  are  selected. 

Mineral  lubricating  oils  are  practically  free  from  any  tendency 
to  oxidize  and  therefore  do  not  gum  or  develop  acid  as  fixed  oils 
do,  which  may  lead  to  corrosion  of  the  bearing  surfaces. 

All  fixed  oils  are  chemical  combinations  of  alcohol  radicles  and 
fatty  acid  radicles.  The  character  of  fatty  acids  is  indicated 
in  Table  No.  2.  The  alcohol  radicle  occurring  in  the  vege- 
table oils  and  most  of  the  animal  oils  is  glyceryl:  C3H5,  which  is 
trivalent,  and  therefore  combines  with  three  fatty  acid  radicles. 
Olein,  for  example,  which  is  the  chief  constituent  of  many  fixed 

TABLE  2. — FATTY  ACIDS  OCCURRING  IN  FIXED  OILS 
(Journ.  Soc.  Chem.  Ind.,  XVIII  (1899),  p.  346) 


Series 

Name  of  acid 

Formula 

Occurs  chiefly  in 

P-! 

Acetic 
CnH2nO2 

Iso  valeric  

Cj  HioO2 
C6  Hi2O2 
C8  H1602 
CioH20O2 
Ci2H24O2 
CnH28O2 

C]6H32O2 

Ci8H36O2 

C20H4002  } 
C24H4802  J 

Porpoise  jaw  oil. 
Cocoanut  oil. 

Palm  oil;  also  tallow,  olive 
oil  and  cocoanut  oil. 
Tallow;   also   palm,   castor 
and  rape  oils. 
Earthnut,    rape    and    mus- 
tard oils. 

Caproic  

Caprylic  
Capric  

Laurie       .... 

Myristic  

Palmitic  
Stearic 

Arachidic  
Lignoceric  

Oleic 
CnH2n-2O2 

Oleic  . 

CisH34O2 

Ci8H34O2  1 
C22H4202  ( 

Olive   oil   and   the   animal 
oleins. 

Rape  oil. 

Rapic  
Erucic  

Linolic 
CnH2n_402 

Linoleic  

C18H32O> 

The  drying  oils;  also  in 
and  palm  oils. 

olive 

Recinoleic 
CnH2n_2Os 

Ricinoleic  

C18H3403  1 

C,8H34O3  j 

Castor  oil. 

Isoricinoleic  .... 

CnH2n04 

Dihydraxystearic  ,  . 

Ci8H36O4 

Castor  oil. 

FIXED  OILS  AND  FATS  17 

oils,  such  as  tallow,  lard,  neatsfoot  and  olive  oils,  has  the  chemical 
formula:  CsHsfCisHssC^s,  in  which  C,  H  and  0  signify 
carbon,  hydrogen,  and  oxygen  atoms  respectively.  Stearin: 
CsEWdsHssC^s  and  Palmitin:  CaHsCCjeHsiC^a  predominate  in 
solid  fats,  olein  in  the  fluid  oils.  It  will  therefore  be  seen  that 
the  nature  of  the  fatty  acid  radicle  determines  the  character 
of  the  fixed  oil. 

Sperm  oil  is  made  up  differently,  being  known  as  a  liquid  wax. 
All  fixed  oils,  however,  can  be  split  up  into  alcohols  and  fatty 
acids,  by  heating  with  water  under  pressure,  by  heating  with 
sulphuric  acid,  by  heating  with  alkalis,  etc.  By  such  actions  the 
fixed  oils  are  said  to  be  saponified.  For  example,  by  heating 
olein  with  water  under  pressure,  the  following  change  takes  place  : 


Olein  Water  Glycerin  Oleic  acid 

This  change  takes  place  in  steam  cylinders,  when  too  high  a 
percentage  of  fixed  oil  is  used  in  the  cylinder  oil;  the  fatty  acids 
thus  liberated  eat  away  the  metal  and  form  metallic  soaps. 

By  heating  olein  with  an  alkali,  potash  for  example,  the  follow- 
ing change  takes  place  : 


Olein  Potash  Glycerin  Potassium  oleate 

It  will  be  seen  that  the  fatty  acid  is  not  now  liberated,  but  has 
combined  with  the  potash  and  formed  a  soap. 

This  action  .  distinguishes  fixed  oils  from  mineral  oils,  which 
are  not  saponified  when  heated  with  an  alkali,  but  remain 
unchanged. 

CHARACTERISTICS  OF  SOME  FIXED  OILS  AND  FATS 

(See  also  Tables  Nos.  3  and  4,  Pages  23  and  24^ 

Vegetable  Oils  and  Fats.  Castor  Oil  (Non-drying).  —  Castor 
oil  is  obtained  from  the  seeds  of  the  castor  tree  or  shrub,  which 
grows  in  all  tropical  and  sub-tropical  countries.  The  kernel 
forms  80  per  cent,  of  the  seed  and  yields  about  50  per  cent,  of 
its  weight  in  oil.  By  cold  pressing  of  the  seeds  medicinal  castor 
is  produced.  By  hot  pressing  "  first  pressings"  and  "  second 
pressings"  are  afterwards  produced.  Castor  oil  may  also  be 
extracted  by  solvents.  Crude  castor  oil  is  refined  by  steaming 
and  filtration.  When  properly  refined  castor  oil  keeps  well  and 
does  not  easily  turn  rancid. 

Castor  oil  is  liable  to  deposit  a  solid  fat  in  very  cold  weather, 
but  congeals  only  at  very  low  temperatures.  It  is  nearly  colorless 


18  PRACTICE  OF  LUBRICATION 

or  slightly  greenish-yellow;  it  has  the  highest  specific  gravity 
and  viscosity  of  all  fixed  oils;  it  is  soluble  in  alcohol  but  not  in 
petroleum  spirit,  nor  does  it  mix  to  any  large  extent  with  mineral 
oils.  It  mixes  with  refined  rosin  oil  in  all  proportions.  It  will 
absorb  a  maximum  of  about  12  per  cent,  of  pale,  low  setting 
point  mineral  lubricating  oil,  whereas  mineral  oil  will  not  absorb 
much  more  than  3  per  cent,  of  castor  oil. 

All  fixed  oils,  except  castor,  mix  readily  with  mineral  oils,  and 
it  is  quite  easy  to  make  clear  mixtures  of  castor  oil  and  mineral 
oil  in  the  presence  of  another  fixed  oil,  such  as  lard  oil  or  rape  oil. 

Castor  oil  is  an  excellent  lubricant,  possessing  great  oiliness. 
It  is  used  for  lubricating  bearings  subjected  to  great  pressure, 
such  as  heavy  type  marine  engines,  and  is  extensively  used  for 
aeroplane  engines,  particularly  the  rotary  types,  which  cannot  be 
lubricated  satisfactorily  with  any  oil  other  than  pure  medicinal 
castor.  It  is  also  used  in  the  manufacture  of  soluble  oils,  in  the 
manufacture  of  greases  for  pistons  with  India  rubber  or  leather 
fittings,  as  a  preservative  for  rubber  and  leather  belting,  etc. 
The  possibilities  of  castor  oil  as  a  lubricant  appear  to  be  far 
from  exhausted.  For  example,  little  work  has  been  done  with 
blown  castor  oil,  nor  does  there  appear  to  be  any  satisfactory 
method  developed  .to  make  miscible  castor  oil.  One  method  is 
to  heat  castor  oil  for  a  few  hours  at  4-5  atmospheres  pressure  ; 
this  treatment  changes  its  nature  and  makes  it  more  miscible 
with  mineral  oil. 

Treated  with  sulphuric  acid,  castor  oil  takes  up  25  per  cent, 
of  water  and  becomes  " Turkey  red"  oil  used  in  preparing  cotton 
fiber  for  dyeing. 

Rape  Oil  (Colza)  (Semi-drying). — Rape  oil  is  obtained  either 
by  expression  or  extraction  from  rape  seed,  grown  chiefly  in 
India  and  Russia.  Crude  rape  is  dark  in  color  and  contains 
slimy  impurities  which  are  removed  by  treatment  with  sulphuric 
acid,  followed  by  agitation  with  steam  and  hot  water.  If  not 
sufficiently  treated  with  acid,  the  slimy  impurities  choke  the 
lubricating  grooves;  it  is  preferable  to  prolong  the  acid  treatment 
and  make  sure  of  the  elimination  of  the  impurities,  notwithstand- 
ing the  development  of  a  little  extra  free  fatty  acid. 

Black  Sea  rape  oil— Ravison  Rape— is  expressed  from  seeds  of 
the  Wild  rape  of  the  Black  Sea  district;  it  is  inferior  to  ordinary 
rape  oil,  being  about  10  per  cent,  lower  in  viscosity  and  having 
a  greater  tendency  to  oxidize  (more  " drying"). 

Blown  rape  oil  is  rape  oil  which  has  been  blown  with  air  at  a 
temperature  rising  during  the  process  from  160°F.  to  250°F. 
The  oil  is  oxidized,  increases  greatly  in  specific  gravity  and  vis- 


FIXED  OILS  AND  FATS  19 

cosity,  and  develops  free  fatty  acid.  The  specific  gravity  may 
be  increased  from  0.915  to  as  much  as  0.985. 

When  rape  oil  is  blown,  the  color  darkens  for  about  3  hours, 
then  the  oil  becomes  pale,  but  at  the  finish  of  the  operation  it 
darkens  to  a  deep  red;  it  gives  off  considerable  odor,  but  the 
finished  oil  has  no  odor.  The  viscosity  at  first  decreases  corre- 
spondingly with  the  pale  color,  then  increases,  becoming  200" 
Saybolt  at  212°F.  after  22  hours,  720"  Saybolt  after  34  hours 
and  so  on. 

Rape  oil  or  blown  rape  oil,  is  chiefly  used  in  the  manufacture 
of  railway  and  marine  engine  oils,  from  10  per  cent,  to  25  per 
cent,  being  mixed  with  heavy  viscosity  (preferably  low  setting- 
point)  mineral  oils  at  a  temperature  of  about  140°F.  Rape  oil 
is  also  used  in  the  manufacture  of  soluble  oils  and  as  a 
quenching  oil  for  steel. 

Rape  oil  mixes  in  all  proportions  with  mineral  oil,  but  with 
blown  rape  oil  there  is  a  minimum  percentage,  below  which  the 
blown  rape  will  not  mix  with  the  mineral  oil.  This  minimum 
percentage  is  less  at  lower  temperatures,  so  that  sometimes  in 
cold  weather  the  blown  oil  separates  out.  The  blown  oil  also 
separates  out,  if  oil  containing  blown  rape  is  diluted  sufficiently 
with  mineral  oil. 

Cottonseed  Oil  (Semi-drying). — Cottonseed  oil  is  obtained  by 
expression  from  cotton  seed .  On  account  of  its  drying  properties, 
it  should  not  be  used  for  lubrication;  it  is  however  often  used  to 
adulterate  olive  oil,  rape  oil  or  lard  oil.  Blown  cottonseed  oil  is 
used  as  a  substitute  for  blown  rape  oil  in  the  manufacture  of 
marine  engine  oils,  but  is  not  to  be  recommended.  As  a  cutting 
oil  it  is  used  to  give  a  high  degree  of  "  finish. " 

Linseed  Oil  (Drying). — Linseed  oil  is  obtained  from  the  seed 
of  flax,  is  pale  yellow  in  color  and  is  the  best  known  of  the  drying 
oils.  It  cannot  be  used  as  a  lubricant. 

Olive  Oil  (Non-drying). — Olive  oil  is  obtained  by  expression 
from  the  fruit  of  the  olive  tree.  Fine  olive  oils  are  pressed  cold 
and  are  used  as  salad  oils  as  well  as  for  lubrication.  Olive  oils 
from  the  second  pressing  (hot)  are  used  for  lubrication,  but  are 
inferior  to  cold  pressed  olive  oil;  they  are  more  inclined  to  "dry" 
contain  a  rather  high  percentage  of  free  fatty  acid,  and  easily 
become  rancid.  Olive  oils  have  now  practically  gone  out  of  use 
for  lubrication,  having  been  displaced  by  mineral  oils  or[mixtures 
of  such  oils  with  rape  oil. 

Olive  oil  is  largely  used  as  wool  oil  in  the  high  class  woollen 
industry;  it  is  unsurpassed  for  this  purpose,  lubricating  the 
woollen  fibers  during  manufacture  and  being  completely  scoured 


20  PRACTICE  OF  LUBRICATION 

out  of  the  yarn  when  completed.  It  is  used  for  lubricating  high 
quality  cloth  looms  or  finishing  machines,  as  if  it  gets  on  to  the 
cloth  the  stains  disappear  entirely  in  the  scouring  process. 

Cocoanut  Oil  (Non-drying}.— Cocoanut  oil  is  produced  from 
cocoanuts,  the  fruits  of  a  certain  kind  of  palm  tree.  The  kernels 
are  cut  up  and  dried  in  the  sun,  producing  the  so-called  "  Copra" 
from  which  cocoanut  oil  is  obtained  by  expression. 

Cocoanut  oil  is  fluid  in  tropical  climates,  solid  in  colder  climates 
the  melting  point  being  70°F.-80°F.  By  cold  pressing  a  fluid, 
cocoanut  oleine,  is  obtained  which  is  used  for  lubricating  pur- 
poses; the  solid  portion  is  used  as  an  edible  fat. 

Cocoanut  oleine  is  used  to  the  extent  of  from  3  per  cent,  to  10 
per  cent,  in  the  manufacture  of  oils  for  internal  combustion 
engines. 

Palm  Oil,  Palm  Kernel  Oil  (Non-drying). — Palm  Oil  and 
Palm  Kernel  Oil  are  obtained  from  the  fruit  of  the  African  oil 
palm.  The  palm  oil  is  produced  from  the  fleshy  layer  or  peri- 
carp surrounding  the  hard  woody  shell,  within  which  is  the  seed 
kernel.  The  palm  kernel  oil  is  produced  from  the  kernels  and 
is  quite  different  from  palm  oil;  it  closely  resembles  cocoanut  oil; 
but  usually  contains  a  large  proportion  of  free  fatty  acid  and  is 
not  used  for  lubrication. 

Palm  oil  varies  in  color  from  yellow  to  deep  red;  the  odor  is 
pleasant;  the  melting  point  ranges  from  80-1 10°F.,  the  higher 
values  corresponding  with  high  percentages  of  free  fatty  acid, 
which  are  present  to  the  extent  of  10  per  cent,  to  40  per  cent, 
or  even  more.  Palm  Oil  is  used  in  the  manufacture  of  railway 
lubricating  greases. 

Peanut  Oil,  Also  Called  Earthnut  Oil,  Ground-nut  Oil,  Arachis 
Oil  (Non-drying). 

This  oil  is  obtained  from  the  nuts  of  a  creeping  plant  called 
Arachis  hypogcea.  It  is  pale  greenish  yellow  in  color,  of  a 
nutty  flavor  and  odor,  but  is  now  made  nearly  colorless  and 
tasteless  for  edible  purposes.  It  contains  about  5  per  cent,  of  free 
fatty  acid  and  is  a  non-drying  oil.  Peanut  oil  is  used  in  the 
same  manner  as  cocoanut-oleine  in  the  manufacture  of  oils  for 
internal  combustion  engines. 

Mustard  Seed  Oil. — Mustard  seed  oil  is  said  to  have  lubricating 
properties  similar  to  those  of  castor  oil,  but  it  does  not  appear  to 
have  been  much  used  as  yet  for  lubrication. 

Rosin  Oil  (Semi-drying). — Rosin  oil  is  produced  by  de- 
structive distillation  of  colophony  (common  rosin).  The  first 
products  distilling  over  are  rosin  spirits.  The  rosin  oil  distils 
over  above  300°C.  (572°F.)  and  may  amount  to  85  per  cent,  of  the 


FIXED  OILS  AND  FATS  21 

total  products.  The  residue  in  the  still  is  rosin  pitch,  or,  if  the 
distillation  is  carried  to  dryness,  coke. 

Crude  rosin  oil  is  a  brown,  viscous  liquid  with  a  strong  blue  or 
violet  fluorescence.  By  heating  to  150°C.  for  three  or  four  hours 
the  fluorescence  changes  to  green  and  it  loses  from  1  per  cent,  to 
5  per  cent,  of  its  more  volatile  constitutents.  It  contains  a  con- 
siderable percentage  of  rosin  acids. 

Pale  rosin  oils  can  be  produced  by  refining  the  crude  rosin  oil. 
The  bloom  can  be  removed  by  sunbleaching  in  shallow  vessels, 
or  by  treatment  with  nitronaphthalene,  hydrogen  peroxide,  etc. 

The  specific  gravity  ranges  from  0.96  to  1.01. 

Rosin  oil  is  no't  used  as  a  lubricant  in  the  ordinary  way,  but 
both  rosin  and  rosin  oil  are  successfully  used  in  the  manufacture 
of  soluble  oils,  belt  dressings,  etc.  It  is  also  used  in  the  manu- 
facture of  low  quality  lubricating  greases. 

Animal  Oils  and  Fats.  Tallow  (Non-drying). — Beef  tallow  is 
obtained  from  cattle;  mutton  tallow  from  sheep  and  goats.  In 
rendering  tallow  for  lubrication,  it  is  important  to  use  only  fresh 
fat,  which  has  not  become  decomposed  and  to  remove  by  settling 
and  straining  all  water  and  membrane. 

Tallow  from  60°F.  to  80°F.  is  a  mixture  of  solid  and  fluid  fats. 
When  used  for  lubrication  it  should  preferably  not  contain  more 
than  4  per  cent,  of  free  fatty  acid.  Beef  tallow  is  less  inclined  to 
become  rancid  than  mutton  tallow. 

Tallow  is  used  in  the  manufacture  of  white  tallow  greases,  also 
in  most  other  lubricating  greases  to  form  the  saponified  base 
which  " holds"  the  lubricating  oil  in  the  grease.  Unrendered 
tallow — suet — is  sometimes  used  for  lubricating  badly  worn, 
open-type  bearings. 

Tallow  Oil  (Non-drying). — If  tallow  is  subjected  to  pressure, 
the  liquid  portion  can  be  separated  out  and  is  known  as  tallow 
oil.  ,  Acidless  tallow  oil  is  carefully  made  tallow  oil  and  is  used 
chiefly  in  the  manufacture  of  steam  cylinder  oils,  the  admixture 
of  tallow  oil  being  from  3  per  cent,  to  15  per  cent.  It  is  also  used 
in  the  manufacture  of  cutting  oils.  It  should  have  a  low  con- 
tent of  fatty  acid  and  a  clean  sweet  odor;  it  should  be  colorless 
or  pale  yellow,  and  free  from  suspended  matter. 

Lard  Oil  (Non-drying). — Lard  oil  is  a  fluid  oil  expressed  from 
pig's  fat.  Winter  pressed  lard  oil  has  a  lower  setting  point  than 
summer  pressed  lard  oil.  The  setting  point  depends  entirely 
upon  the  temperature  at  which  the  oil  has  been  pressed;  it  may 
range  from  32°F.  to  60°F. 

Prime  lard  oil  is  nearly  colorless  or  pale  yellow. 

Tinged  lard  oil  is  a  second  quality  lard  oil,  being  more  or  less 


22  PRACTICE  OF  LUBRICATION 

colored  (yellow  to  brownish  red)  and  containing  a  high  percent- 
age of  free  fatty  acid,  from  8  per  cent.,  to  15  per  cent,  or  more. 

The  best  grades  of  lard  oil  are  used  in  the  manufacture  of 
cutting  oils  (5  per  cent,  to  100  per  cent,  lard  oil);  in  the  manu- 
facture of  internal  combustion  engine  oils  (3  per  cent,  to  10  per 
cent,  lard  oil);  also  in  the  manufacture  of  stainless  oils.  Tinged 
lard  oil  is  nearly  always  used  instead  of  prime  lard  oil  in  making- 
cutting  oils,  but  not  in  a  greater  proportion  than  15  per  cent,  to 
25  per  cent.  on.  account  of  its  bad  odor  and  greater  gumming 
tendency  than  prime  lard. 

Neatsfoot  Oil  (Non-drying). — Neatsfoot  oil  is  obtained  by 
boiling  the  hoofs  and  bones  of  cattle  in  water  and  skimming  off 
the  oil  from  the  surface.  When  the  oil  is  chilled  and  pressed,  a 
low  setting  point  neatsfoot  oil  is  produced,  which  is  much  used 
for  lubrication  of  watches  and  scientific  instruments;  it  is  used 
for  lubricating  the  air-operated  engines  in  torpedoes;  also  for 
lubricating  lace-making  machinery  on  account  of  its  clinging 
and  stainless  properties.  The  high  price  of  neatsfoot  oil  has 
confined  its  use  as  a  lubricant  to  such  special  purposes. 

Neatsfoot  oil  in  its  general  properties  resembles  lard  oil  and  is 
largely  used  for  treating  leather. 

Sperm  Oil  (Non-drying). — Southern  sperm  is  obtained  from 
the  head  or  blubber  Of  the  cachelot  whale,  which  is  generally 
found  in  tropical  or  temperate  seas.  A  large  cavity  in  the  head 
of  the  whale  is  filled  with  crystalline  matter  called  "  Spermaceti. " 
Arctic  sperm  is  obtained  from  the  blubber  of  the  bottlenosed 
whale,  which  is  found  in  the  Northern  seas,  hence  the  name, 
Arctic  sperm. 

The  crude  sperm  oil  is  cooled,  so  that  most  of  the  spermaceti 
separates  out,  then  pressed.  The  spermaceti  is  used  for  making 
candles. 

Sperm  oil  has  only  a  slight  tendency  to  oxidize,  a  low  setting 
point,  and  the  lowest  viscosity  and  specific  gravity  of  all  fixed 
oils.  It  is  a  valuable  lubricant  for  high  speed  spindles  in  textile 
mills;  being  generally  used  mixed  with  low  viscosity  mineral 
oils  (5  per  cent,  to  25  per  cent,  sperm). 

Whale  Oil  (Semi-drying)  .—Whale  oil  is  obtained  from  the 
blubber  of  the  Greenland  and  other  whales.  The  specific  gravity 
of  whale  oil  is  much  higher  than  that  of  sperm  oil.  Whale  oil 
has  marked  drying  properties,  but  the  pale  grades  are  used 
successfully  as  lubricants  when  mixed  in  small  proportions  (5  per 
cent,  to  10  per  cent.)  with  mineral  spindle  oils  for  textile  purposes 
or  as  cutting  oils.  Dark  whale  oils  are  lower  in  quality  and  can- 
not be  used  for  lubrication  but  are  excellent  as  tempering  or 


FIXED  OILS  AND  FATS 


23 


quenching  oils  used  in  the  manufacture  of  tools,  guns,  case- 
hardened  materials,  etc. 

Seal  oil  is  similar  to  whale  oil  and  is  obtained  from  the  blubber 
of  seals. 

Porpoise  Jaw  Oil,  Dolphin  Jaw  Oil  and  Melon  Oil  (Non-dry- 
ing).— These  oils,  which  are  very  similar,  are  obtained  from  the 
soft  fat  of  the  head  and  jaw  of  the  porpoise  and  the  dolphin. 

Melon  oil  is  made  from  a  melon  shaped  lump  of  fat  in  the  head 
of  the  dolphin;  the  crude  oils,  obtained  in  the  usual  way,  are 
chilled  and  pressed  to  remove  solid  fat.  These  oils  are  used 
particularly  in  the  United  States  for  lubricating  watches  and 
other  delicate  mechanism,  and  command  a  high  price. 

Menhaden,  Cod  or  Other  Fish  Oils  (Semi-drying). — Menhaden, 
cod  or  other  fish  oils  are  obtained  by  boiling  fish  in  large  pans 
with  steam;  after  standing  some  time  the  oil  rises  to  the  surface 
and  can  be  skimmed  off.  The  color  varies  according  to  the 
freshness  of  the  fish  and  the  length  of  boiling. 

Fish  oils  are  chiefly  used  in  the  leather  industry,  but  blown 
cod  oil,  blown  in  a  similar  manner  to  blown  rape  oil  and  to  similar 
viscosities,  has  given  fair  satisfaction  in  the  manufacture  of 
marine  engine  oils.  Fish  oils  have  also  been  used  as  quenching 
and  tempering  oils. 

TABLE  3. — CHARACTERISTICS  OP  FIXED  OILS  AND  FATS 


Specific 
gravity 

Setting 
point 
in°F. 

Open 
flash- 
point 
in°F. 

Iodine 
value 

Saponifi- 
cation 
value 

Per 
cent, 
of  free 
fatty 
acid 

Drying 
char- 
acter 

Castor  oil  

.960-   .966 

0-10 

530-560 

80-90 

176-186 

.1-6 

Non 

Rape  oil  

.913-    .916 

12-26 

530-560 

96-108 

170-176 

.3-3 

Semi 

Ravison  rape  
Blown  rape     

.918-   .922 
.960-    .985 

108-120 

178-179 

2-6 

Semi 
S6mi 

Cottonseed  oil  

.921-    .926 

32 

560-625 

100-120 

192-195 

Semi 

Linseed  oil  
Olive  oil  

.931-    .936 
.915-    .918 

-  15-10 
20-50 

550 

475-600 

170-200 
80-90 

192-195 
185-196 

.4-4 
3-20 

Drying 
Non 

Cocoanut  oleine.  .  .  . 
Palm  oil  

.925-    .930 
.922-    .925 

40-70 
80-110 

530 
450 

8-9 
50-56 

250-260 
196-202 

2-20 
10-60 

Non 
Non 

Peanut  oil  

.918-    .925 

27-37 

540-620 

90-102 

187-191 

1-5 

Non 

Tallow,  beef  or  mut- 
ton    

.935-    .950 

100-125 

550-590 

34-48 

195 

2-10 

Non 

Tallow  oil  

.913-    .918 

32-40 

540-600 

55-60 

195 

1-5 

Non 

Lard  oil  

.914-    .918 

32-60 

500-600 

65-75 

195 

3-25 

Non 

Neatsfoot  oil  

.914-    .917 

0-40 

470-580 

65-75 

195 

.2-25 

Non 

Sperm  oil  

.878-    .882 

32 

505 

80-94 

120-140 

.5-3 

Non 

Whale  oil  

.924-   .925 

40-50 

475 

110-130 

187-197 

2-10 

Semi 

Porpoise  jaw  oil.  . 

.916-    .927 

22-48 

.... 

Non 

Menhaden  oil  

.930-    .933 

20-25 

530 

140-170 

*191 

3-6 

Semi 

Cod  oil,  fish  oil  

.921-    .928 

20 

470 

145-170 

*189 

1-15 

Semi 

Rosin  oil  

.960-1  01 

360 

25-115 

70-80 

0-35 

Non  to- 

semi 

Wool  grease.  

.944-    .960 

100-130 

450 

15-30 

*100 

50-60 

Non 

*  Single  values  only. 


24 


PRACTICE  OF  LUBRICATION 


Wool  Grease. — Wool  grease  is  obtained  in  the  process  of  wool- 
washing;  the  alkaline  scouring  liquors  containing  the  wool 
grease  are  run  into  settling  tanks;  the  fatty  matter  accumulating 
on  the  surface  is  collected  and  drained  in  filter  bags.  The  scour- 
ing liquors  may  also  be  treated  with  sulphuric  acid  in  conjunction 
with  injection  of  live  steam;  the  acid  separates  the  fatty  matter 
and  three  distinct  layers  are  formed;  greasy  matter  on  the  top, 
water  and  soda  in  the  middle,  and  earthy  matter  at  the  bottom. 

The  extracted  grease  is  dirty  and  contains  water;  the  water  is 
removed  by  cold  and  hot  pressing,  followed  by  strong  sulphuric 
acid  treatment.  The  wool  grease  thus  prepared  is  known  to  the 
trade  as  " Yorkshire  Grease"  and  is  used  in  the  manufacture  of 
rolling  mill  greases,  railway  and  colliery  greases. 

On  the  Continent  a  process  of  wool  cleansing  by  means  of 
solvents  (ether  or  carbon  bisulphide)  is  often  employed;  the 
solvents  are  afterward  recovered  by  distillation  and  the  wool 
grease  remains  behind.  Such  wool  grease  is  usually  distilled 
with  superheated  steam,  and  produces  woololein  and  woolstearin, 
etc.  One  use  of  woololein  is  in  the  manufacture  of  wool  oils. 

TABLE  4. — VISCOSITIES  OF  SOME  FIXED  OILS  AND  FATS 


Saybolt  viscosity,  seco  nds 

At  104°F. 

At  212°F. 

Castor  oil  .... 

- 
1100-1200 
240 

90-100 
57 
52-54 
50-53 
50 
41-45 
38 

Rape  oil  

Tallow,  beef  or  mutton  

Lard  oil,  neatsfoot  oil,  olive  oil,  peanut  oil 

190-220 
170 
135-155 
106 

Cottonseed  oil  

Cocoanut  oil,  whale  oil,  cod  oil,  Menhaden  oil  ... 
Sperm  oil  .  . 

CHAPTER  III 
SEMI-SOLID  LUBRICANTS 

Semi-solid  lubricants  are  lubricants  which  do  not  flow  at 
ordinary  room  temperatures.  Animal  or  vegetable  fats,  such 
as  tallow  or  palm  oil,  or  poor  cold  test  cylinder  stock  may  be 
classified  as  semi-solid  lubricants.  Most  semi-solid  lubricants 
are,  however,  made  from  mineral  oils  and  saponified  fats  or 
fixed  oils,  and  may  be  divided  into  two  main  groups,  i.e.,  cup 
greases,  and  solidified  oils  or  fats. 

Cup  greases  are  boiled  greases  and  consist  of  80  per  cent. 
to  90  per  cent,  of  mineral  oil  mixed  homogeneously  with  10  per 
cent,  to  20  per  cent,  of  saponified  :fat,  preferably  clarified  beef 
tallow.  The  tallow  is  mixed  with  limewater  and  heated  in  a 
steam-jacketed  kettle  (60  to  90  Ib.  steam  pressure)  for  three 
to  four  hours  until  the  base  for  the  grease  is  completely  formed. 
The  mineral  oil  is  gradually  (5  to  6  hrs.)  mixed  with  the  base 
until  the  right  consistency  of  the  grease  has  been  obtained,  the 
mixture  being  constantly  agitated  mechanically  or  by  compressed 
air. 

The  grease  is  then  run  out  during  the  next  couple  of  hours, 
during  which  time  the  consistency  becomes  gradually  softer 
due  to  the  agitation,  notwithstanding  that  the  speed  of  the  stirrers 
is  reduced  towards  the  finish.  Some  manufacturers  run  the 
grease  out  of  the  boiling  kettle  into  a  grinding  mill,  in  which  all 
lumpy  matter  and  impurities  are  reduced  and  the  grease  made 
of  a  uniform  consistency  (the  more  the  grease  is  kneaded  the 
softer  it  becomes). 

Grinding  the  impurities  fine  does  not,  however,  remove  them; 
it  is  better  to  strain  the  grease  when  it  leaves  the  kettle.  This  is 
best  done  by  forcing  the  grease,  when  hot  and  fluid,  under  great 
pressure  through  fine  layers  of  gauze.  The  gauze  retains  all  the 
impurities,  so  that  the  grease  is  perfectly  clean  when  filled  into 
the  packages.  It  is  surprising  to  see  the  amount  of  impurities 
that  can  be  retained  in  this  way  from  grease  which  one  might 
consider  practically  clean. 

The  ideal  amount  of  grease  made  in  one  batch  is  20  to  25 
barrels. 

Cup  greases  should  be  free  from  fillers,  such  as  chalk,  china  clay^ 

25 


26  PRACTICE  OF  LUBRICATION 

gypsum  (sulphate  of  calcium),  barytis  (sulphate  of  barium), 
asbestos,  talc,  wax,  etc.;  they  should  be  free  from  uncombined 
lime,  gritty  impurities,  rosin  oil,  rosin  or  resinates,  free  from  min- 
eral or  fatty  acids,  alkalies  or  deleterious  impurities;  the  yield 
of  ash  should  be  less  than  2  per  cent,  for  a  medium  grease  and 
less  than  3  per  cent,  for  a  hard  grease;  the  contents  of  water 
should  be  less  than  2  per  cent. 

The  melting  points  of  ordinary  cup  greases  range  from  75° C. 
to  95°C.,  being  higher  for  the  harder  consistency  greases  than  for 
the  softer  greases. 

The  consistencies  of  greases  range  from  very  soft  to  very  hard 
and  are  frequently  indicated  by  numbers,  as  follows : 

No.  1  No.  2  No.  3  No.  4  No.  5 

Very  soft  Soft  Medium  Hard  Very  hard 

The  softer  the  grease  the  more  oil  does  it  contain. 

The  mineral  oils  used  for  making  cup  greases  are  pale  mineral 
oils  (pale  to  give-  the  grease  a  light  color).  Red  oils  might  quite 
well  be  used;  the  drawback  is  that  they  do  not  give  the  grease 
such  a  nice  appearance  as  the  pale  oils.  The  viscosities  of  the 
mineral  oils  used  range  from  150"  to  1200"  at  70°F. 

Graphite  lubricating  grease  is  cup  grease  which  has  been  mixed 
with  from  5  per  cent,  to  20  per  cent,  of  amorphous  or  flake 
graphite. 

Cold  neck  greases  are  black  lime  greases  made  with  black  heavy 
viscosity  oils  and  are  used  for  lubricating  "cold"  rolling  mill 
necks  in  steelworks. 

Fibre  greases  are  of  a  "fibrous"  nature,  but  contain  no  fibres 
of  any  kind.  They  are  usually  made  by  saponifying  a  fixed 
oil  with  caustic  potash,  or  caustic  soda  and  a  little  water.  After 
saponification  the  water  is  boiled  out  and  the  mineral  oil  is 
worked  in.  Fibre  greases  of  good  quality  can  be  melted  and 
cooled  again  without  altering  their  consistency. 

Some  fibre  greases  have  very  high  melting  points,  ranging  from 
145°C.  to  260°C. 

Solidified  oils  or  fats  are  made  in  a  similar  manner  to  cup 
greases,  but  are  made  cold  and  with  carbonate  of  soda  or  caustic 
soda  as  the  saponifying  agent  in  place  of  lime  water.  These 
greases  may  be  made  in  small  quantities,  as  it  is  only  a  question 
of  mixing  the  right  proportions  of  the  various  ingredients  to- 
gether, cold  or  at  fairly  low  temperature,  and  stirring  the  mixture 
till  it  sets.  It  is  obvious  that  the  ingredients  cannot  be  so  per- 
fectly mixed  and  combined  as  with  cup  greases  which  are  boiled; 
the  result  is  that  certain  parts  of  the  grease  will  often  contain 
excess  soda,  which  is  detrimental  to  good  lubrication. 


SEMI-SOLID  LUBRICANTS  27 

Many  so-called  soap  thickened  oils  are  a  kind  of  solidified 
oil,  various  soaps  being  added  to  a  mineral  oil.  Sometimes 
special  " thickeners"  are  sold  for  the  purpose  of  increasing  the 
viscosity  of  mineral  oils;  aluminum  soap  for  example  is  used, 
consisting  of  20  per  cent,  aluminum  oleate  or  palmitate  and  80 
per  cent,  mineral  oil,  in  which  the  soap  is  dissolved.  Mineral  oils 
thickened  with  aluminum  soap  have  a  peculiar  non-homogeneous 
nature;  the  viscosity  is  unstable  and  the  oil  is  of  a  slimy  nature, 
forming  threads  when  dropping.  In  contact  with  water  and 
steam  the  aluminum  soap  is  precipitated  and  clogs  the  machinery. 

White  greases  are  usually  made  from  animal  fat  and  a  small 
amount  of  mineral  oil,  solidified  by  soap.  The  melting  points 
are  lower  than  the  melting  points  of  cup  grease,  ranging  from 
45°C.  to  70°C. 

Certain  white  greases  contain  finely  pulverized  mica  and  are 
sold  under  the  name  of  mica  greases. 

Railway  Wagon  Grease. — The  yellow  grease  used  in  the  axle 
boxes  of  railway  wagons  is  usually  composed  of  tallow,  palm 
oil,  soda-soap  and  water. 

•  According  to  a  number  of  formulae  quoted  by  Mr.  Archbutt, 
the  specifications  are  approximately  as  follows : 

Saponifiable  oils 30  to  45  per  cent.,  occasionally  partly 

replaced  by  mineral  oil. 

Anhydrous  soap 10  to  30  per  cent. 

Water 40  to  60  per  cent. 

Insoluble  matter 0.02  to  2.8  per  cent. 

Usually  3  per  cent,  to  5  per  cent,  more  water  is  used  in  the 
winter  greases  than  in  the  summer  greases. 

A  good  wagon  grease  should  melt  at  -about  40°C.  without  sepa- 
rating; cup  greases  are  unsuitable  for  railway  wagons,  as  they 
have  too  high  melting  points  and  when  continuously  exposed  to 
high  temperature  in  the  axle  boxes  the  oil  separates  out,  leaving 
the  soap  behind. 

Rosin  grease  is  made  by  stirring  together  rosin  oil,  slaked  lime 
and  usually  black  mineral  oil  or  neutral  coal  tar  oil. 

The  rosin  acids  present  in  the  rosin  oil  combine  with  the  lime 
forming  a  soap,  which  solidifies  the  mixture  of  the  various  oils. 
Water  to  the  extent  of  up  to  20  per  cent,  is  sometimes  present 
in  rosin  greases.  • 

Rosin  greases  are  used  to  lubricate  rough  machinery  in  col- 
lieries and  steelworks. 

Hot  neck  greases  are  very  hard  greases  made  from  heavy  resi- 
dues such  as  wool  pitch,  stearine  pitch,  petroleum  pitch,  heavy 
asphaltic  base  petroleum  lubricating  oils — thickened  with  soap 


28  PRACTICE  OF  LUBRICATION 

or  rosin  grease  and  containing  finely  pulverized  talc  or  graphite. 
Hot  neck  greases  are  used  for  lubricating  "hot "  rolling  mill  necks 
in  tinplate  works  and  steelworks. 

Pinion  greases  are  closely  related  to  hot  neck  greases;  they 
frequently  contain  pine  tar  oil  and  are  very  sticky  and  adhesive. 

Special  Greases. — Gear  grease  can  be  made  by  mixing  a  heavy 
viscosity  mineral  oil  with  fibre  grease,  or  with  paraffin  wax. 
Such  mixtures  are  reasonably  stable  when  used  in  the  gear  boxes 
of  motor  cars. 

Solidified  oils  are  not  satisfactory  as  gear  greases,  nor  are  those 
cup  greases  the  bases  for  which  have  been  made  from  rape  oil 
or  cottonseed  oil.  Such  greases  have  too  high  melting  points, 
separate  under  heat,  and  the  soap  which  is  left  cakes  and  carbon- 
izes. Cup  greases  made  from  a  tallow  lime  base  give  reasonable 
satisfaction,  but  are  also  too  high  in  melting  point  and  inclined 
to  cake. 

Yarn  grease  is  a  mixture  of  ordinary  cup  grease  or  fibre  grease 
and  cotton  waste  or  woollen  yarn,  preferably  the  latter.  The 
strands  should  not  be  too  long;  IJ^"  to  2^"  is  a  suitable  length; 
longer  strands  get  entangled  and  it  becomes  difficult  to  divide 
the  grease  when  applying  it  to  bearings. 

Black  floating  grease  is  made  by  mixing  dark  heavy-viscosity 
lubricating  oils  with  powdered  talc,  in  about  even  proportions; 
this  grease  is  still  used  in  some  collieries  as  a  car  grease.  It  is 
low  in  price  and  causes  great  friction  and  wear,  but  the  bearings 
rarely  seize  or  get  scored. 

Petroleum  grease  is  either  a  petroleum  jelly  (see  page  9)  or 
a  mixture  of  petroleum  jelly  with  thin  mineral  oil;  these  greases 
have  low  melting  points  and  little  lubricating  value,  but  they 
contain  no  moisture  and  are  for  that  reason  recommended  by 
several  makers  of  small  ball  and  roller  bearings. 

Scented  Grease. — Many  greases — cup  grease,  solidified  oil,  etc.— 
particularly  when  made  from  rancid  fats  or  fatty  oils  are  scented 
with  oil  of  citronella  or  with  nitro-benzine  to  cover  up  the  bad 
odor.  Such  scenting  should  be  discouraged,  as  it  is  difficult  to 
know  whether  a  scented  grease  is  of  good  or  bad  quality. 


CHAPTER  IV 

SOLID  LUBRICANTS 

Several  kinds  of  solid  materials  are  used  for  lubricating;  pur- 
poses, such  as  graphite,  talc,  soapstone,  mica,  flowers  of  sulphur, 
white  lead,  etc.  Some  of  these  solid  lubricants,  as  flake  graphite 
or  mica,  possess  a  tough  flakey  foliated  structure  which  enables 
them  to  resist  pressure  without  disintegration.  Others,  such  as 
amorphous  graphite  or  flowers  of  sulphur,  are  easily  crushed  into 
a  fine  powder  when  exposed  to  pressure. 

Again,  solid  lubricants  may  be  so  finely  divided  as  to  enable 
them  to  be  suspended  in  colloidal  form  in  a  liquid  carrier.  The 
colloidal  graphite  preparations,  aquadag  and  oildag,  made  by 
Dr.  Acheson's  process,  are  examples  of  such  lubricants,  being 
diffusions  of  colloidal  graphite  in  water  and  oil  respectively. 

CHARACTERISTICS  OF  SOLID  LUBRICANTS 

Graphite. — Graphite  is  the  most  important  of  all  solid  lubri- 
cants. It  is  not  attacked  by  acids  or  alkalis,  nor  affected  by 
high  or  low  temperatures. 

Graphite  is  also  called  " black  lead"  or  " plumbago, "  but  these 
names  are  slowly  going  out  of  use.  Before  the  true  chemical 
nature  of  graphite  was  established  as  being  pure  carbon,  it  was 
thought  that  it  contained  lead,  and  it  was  called  " black  lead"  in 
consequence. 

Natural  Graphite. — The  greater  part  of  the  world's  supplies 
of  natural  graphite  comes  from  Austria,  Ceylon,  Italy,  Bavaria, 
Madagascar,  the  United  States,  Canada,  Mexico,  Japan,  Siberia, 
and  England. 

Natural  graphite  is  found  in  two  forms — flake  graphite  and 
amorphous  graphite;  the  former  is  of  a  tough,  flakey  structure 
and  has  a  pronounced  lustre,  whereas  the  amorphous  graphite 
has  no  such  lustre. 

Natural  graphite,  as  it  is  obtained  from  the  graphite  mines, 
contains  some  impurities,  chiefly  silica,  alumina  and  ferric  oxides. 
Three  methods  of  purification  are  employed  which  may  be 
classified  as  hand  sorting,  mechanical  (dry  or  wet  method),  and 
chemical. 

29 


30  PRACTICE  OF  LUBRICATION 

The  specific  gravity  of  natural  graphite  (2.2)  and  some  of  its 
impurities  are  so  nearly  identical  that  it  is  difficult  to  remove  the 
impurities  completely  by  mechanical  means.  For  this  reason, 
ingredients  like  mica  and  talc  usually  remain  associated  with 
purified  natural  graphite  to  a  greater  or  less  extent  according  to 
the  process  employed. 

It  is  said  that  it  is  easier  to  purify  the  flake  variety  of  natural 
graphite  than  the  amorphous  form;  it  is  unquestionably  a  fact 
that  most  of  the  natural  graphite  employed  for  lubricating  pur- 
poses is  of  the  flake  variety.  The  flake  formation  is  retained 
even  if  it  be  ground  into  a  fine  powder.  It  is  manufactured  in 
several  degrees  of  fineness,  as  for  example  by  the  Joseph  Dixon 
Crucible  Co.  who  obtain  a  high  grade  natural  graphite  from  their 
Ticonderoga  mines,  which  is  practically  free  from  impurities. 

Several  grades  of  flake  graphite  of  British  manufacture  and 
marketed  by  the  Graphite  Products,  Ltd.,  have  been  analzyed 
by  L.  Archbutt,  as  shown  later;  it  is  evidently  possible  to 
produce  commercially  a  graphite  practically  free  from  impurities. 

Flake  graphite  may  be  used  either  dry,  or  in  admixture  with 
semisolid  lubricants.  It  cannot  be  used  mixed  with  oil  in  ordi- 
nary lubricators  or  lubricating  systems,  because  of  its  high  speci- 
fic gravity,  which  causes  it  to  separate  out  and  choke  lubricators, 
oil  pipes  and  oil  grooves. 

Artificial  Graphite. — Amorphous  graphite  is  produced  artifi- 
cially by  Dr.  Acheson  in  the  electrical  furnace.  He  is  able  by 
his  process  to  produce  graphite  of  a  soft,  unctuous,  non-coalescing 
nature  and  almost  chemically  pure. 

The  varieties  produced  for  lubricating  purposes  are  guaranteed 
to  contain  99  per  cent,  of  pure  carbon,  but  usually  contain 
more.  In  one  variety  of  graphite,  No.  1340,  98  per  cent,  of  the 
graphite  particles  are  less  than  J^g  of  an  inch  in  diameter. 
From  this  or  similar  graphite  Dr.  Acheson  produces  what  he 
calls  deflocculated  graphite  by  kneading  it  for  a  long  time  with 
water  in  the  presence  of  a  vegetable  extract,  such  as  tannic  acid. 
The  graphite  particles  in  this  process  disintegrate  into  particles 
one  thousand  times  less  in  diameter;  in  fact,  Dr.  Acheson 
estimates  that  each  particle  of  the  "1340"  graphite  becomes 
divided  into  700,000  particles,  a  smallness  of  size  bordering  on 
the  molecular.  The  graphite  becomes  diffused  in  the  water  in 
colloidal  form  and  each  particle,  being  protected  by  an  envelope 
of  organic  colloidal  matter,  remains  in  suspension  for  an  indefinite 
time  in  the  water. 

Dr.  Acheson  manufactures  the  colloidal  solution  of  graphite  in 
water  in  the  form  of  a  concentrated  paste  under  the  name  of 


SOLID  LUBRICANTS  31 

"aquadag. "  It  may  be  diluted  by  the  addition  of  pure  water 
to  the  required  strength  without  the  graphite  separating  out. 
By  a  further  process  the  concentrated  aquadag  is  mixed  and 
kneaded  with  mineral  lubricating  oil  until  all  the  water  is  re- 
placed by  oil;  this  product  is  called  "oildag, "  and  may  be  diluted 
with  good  quality  neutral  mineral  oil  without  any  appreciable 
separation  of  the  graphite,  without  "  flocculation, "  as  Dr. 
Acheson  calls  it. 

In  Germany,  colloidal  solutions  of  graphite  have  been  produced 
commercially  by  E.  de  Haen,  similar  to  aquadag  and  oildag,  the 
corresponding  names  being  hydrosol  (corresponding  to  aquadag) 
and  oleosol  or  kollag  (corresponding  to  oildag).  These  German 
products  are  made  from  natural  graphite  by  suitable  corrosion 
" stabilizing, "  etc.,  and  from  an  examination  by  Prof.  D. 
Holde  of  Berlin,  they  appear  to  have  the  same  stability  (when 
diluted  with  water  or  oil  respectively)  as  the  colloidal  artificial 
graphites  made  by  Dr.  Acheson's  process.  According  to  Prof. 
Holde,1  in  both  forms  of  colloidal  graphites  there  are  graphite 
particles  of  a  size  from  I/*  to  6/z  but  the  majority  are  submicrons, 
less  than  I/*  in  size  (I/*  equals  0.001  m.m.)  which  are  not  easily 
separated  out  by  centrifuging,  whereas  the  larger  particles  from 
IP  to  QJJ,  are  easily  separated  out  in  this  manner. 

Prof.  Holde  found  that  by  dissolving  oleosol  in  benzol  and 
filtering  it  through  finely  powdered  bleaching  earth,  such  as 
Fuller's  earth,  all  the  graphite  was  retained  in  the  earth,  which 
owing  to  its  absorbing  properties  acted  as  an  ultrafilter,  although 
the  action  was  different  from  the  mechanical  pore  action  of  the 
ultrafilter.  - 

Colloidal  solid  lubricants  may  be  produced  from  materials  other 
than  graphite.  It  will  appear  that  some  successful  attempts 
have  been  made  with  talc  and  mica. 

Talc. — Talc  consists  of  hydrogen  magnesium  silicate  (H2Mg3- 
Si4Oi2)  and  occurs  as  foliated  or  scaly  compact  masses.  Its 
specific  gravity  ranges  from  2.6  to  2.8. 

The  term  Steatite  is  restricted  to  the  compact  massive  varieties 
of  talc. 

Soapstone  is  an  impure  form  of  steatite. 

French  Chalk  is  talc  or  steatite  in  powder  form. 

Talc  scales  feel  greasy  or  soapy,  possess  a  perfect  micaceous 
cleavage,  have  a  pearly  to  silvery  lustre,  and  are  flexible  but  not 
elastic,  thus  differing  from  mica. 

Talc  is  very  soft  and  can  readily  be  scratched  with  the  finger 
nail;  it  is  selected  as  No.  1  in  Mohs's  hardness  scale,  although  the 

1  Zeitschrift  f.  Elecktrochemie  (1917)  2Kis« 


32  PRACTICE  OF  LUBRICATION 

harder  varieties  of  talc  may  have  a  hardness  of  2.5  to  4.  The 
color  of  talc  varies  from  silvery  white  for  the  best  and  softest 
varieties  to  greyish  or  greenish  for  the  harder  steatite  varieties. 

Talc  resists  acids  and  alkalis  and  also  heat  (no  water  being 
lost  below  a  red  heat)  and  cold.  It  is  obtained  chiefly  from  the 
United  States,  but  is  found  also  in  many  countries  such  as  Corn- 
wall, Bavaria,  France,  Italy,  Austria,  and  India. 

Mica. — The  name  "mica"  is  applied  to  a  group  of  minerals 
characterized  by  the  facility  with  which  they  split  into  thin 
lamina  which  are  flexible  and  more  or  less  elastic.  The  hard- 
ness of  the  micas  is  between  2  and  3,  while  their  specific 
gravity  ranges  from  2.7  to  3.1. 

The  chemical  composition  is  subject  to  considerable  variations 
in  different  species — broadly  speaking,  there  is  a  group  of  potash 
micas,  generaly  pale  in  color  and  a  group  of  magnesium  or  ferric 
magnesia  micas,  usually  dark  in  color. 

All  the  micas  are  complex  silicates  containing  aluminum  and 
potassium  generally  associated  with  magnesium  but  rarely  with 
calcium. 

Water  is  always  present  and  many  micas  contain  fluorine. 

Mica  is  prepared  for  the  market  by  splitting  the  blocks  of 
rough  mica  into  plates  which  are  cut  into  the  required  patterns 
by  means  of  shears. 

The  refuse  mica  when  finely  ground  forms  the  material  used  for 
lubricating  purposes.  The  small  particles  of  mica  still  retain 
their  thin  lamellar  structure. 

Flowers  of  Sulphur. — Flowers  of  sulphur  is  not  used  much  for 
lubricating  purposes,  but  is  used  to  some  extent  for  curing  hot 
bearings.  It  is  a  fine  powder  consisting  of  pure  sulphur 
largely  in  the  form  of  minute  crystals.  The  specific  gravity 
is  approximately  2. 

White  Lead. — White  lead  is  used  to  some  small  extent  for  curing 
hot  bearings.  It  is  an  extremely  fine  powder  consisting  chemi- 
cally of  basic  carbonate  of  lead,  generally  said  to  have  the  follow- 
ing formula: 

2PbCO3-Pb(OH)2 


CHAPTER  V 
TESTING  LUBRICANTS 

In  the  early  days,  when  mineral  lubricating  oils  were  nearly  all 
made  from  Pennsylvania  or  Russian  crudes,  only  a  few  varieties 
were  manufactured,  and  simple  physical  and  chemical  tests 
sufficed  to  identify  the  oil.  This  state  of  affairs  no  longer  exists; 
lubricating  oils  are  now  made  from  a  great  variety  of  crudes,  and 
great  experience  is  required  to  judge  the  merits  of  an  oil  on  the 
basis  of  a  laboratory  analysis. 

The  selection  of  an  oil  for  certain  engines  or  machinery  requires 
many  years  of  experience  in  comparing  and  testing  different 
lubricants  under  actual  running  conditions.  Laboratory  tests 
and  investigations  alone  are  of  no  avail,  as  chemists  usually 
have  no  engineering  experience;  on  the  other  hand  lubricating 
engineers  cannot  develop  their  experience  and  judgment  without 
the  very  best  chemical  assistance;  in  fact,  it  is  only  by  co-ordi- 
nating field  engineering  experience  with  careful  laboratory  investi- 
gations that  it  is  possible  to  accumulate  the  kind  of  knowledge 
which  is  required  to  enable  one  to  give,  sound  recommendations 
as  to  the  grades  of  lubricants  which  should  be  selected  for  a 
given  purpose,  as  well  as  the  best  methods  of  application  and  use. 

It  is  a  well-known  fact  that  the  vast  majority  of  oil  firms  op- 
erate on  the  principle  of  getting  samples  of  oils  in  use,  analyzing 
these  samples  more  or  less  roughly,  and  then  offering  oils  more 
or  less  similar  in  character.  As  the  customer  in  most  cases  does 
not  trouble  much  about  the  quality  of  the  oils,  as  long  as  "the 
price  is  right,"  and  as  long  as  nothing  serious  happens  to  his 
machinery,  the  prevailing  standard  of  lubrication  is  usually 
exceedingly  low.  The  author,  who  for  many  years  has  been  in 
charge  of  a  large  staff  of  lubrication  engineers,  can  testify  that 
very  few  works  exist  where  a  lubricating  engineer,  after  a  thor- 
ough works  inspection,  cannot  point  out  means  by  which  great 
economies  can  be  affected  from  the  point  of  view  of  saving  in 
power  (with  all  its  attendant  benefits),  saving  in  lubricants, 
greater  safety  of  operation,  etc.,  all  due  to  better  lubricants  or 
better  methods  of  handling  them  from  the  moment  they  are 
received  at  the  stores  till  the  moment  the  last  drop  has  been  con- 
sumed in  the  works. 

Jt  should  not  be  necessary  for  a  capable  lubricating  engineer 

33 


34  PRACTICE  OF  LUBRICATION 

to  have  samples  of  the  lubricants  in  use  in  order  to  recommend 
the  correct  grades  of  his  firm's  products.  His  general  lubrication 
knowledge  of  engines  and  machinery  and  his  observations  during 
the  inspection  ought  to  be  sufficient  for  that  purpose.  But  if  he 
is  to  give  an  accurate  estimate  of  the  possible  saving  in  power 
or  consumption  to  be  obtained  by  introducing  better  or  more 
suitable  lubricants,  then  an  analysis  of  the  lubricants  in  use  and 
of  the  consumption  in  all  departments  is  required. 

Speaking  generally,  in  order  to  satisfy  certain  lubricating  re- 
quirements, the  lubricant: 

1.  Must  possess  sufficient  viscosity  and  lubricating  power — 
oiliness — to  suit  the  mechanical  conditions  and   conditions   of 
speed,  pressure  and  temperature. 

Too  little  oiliness  means  excessive  wear  and  friction;  too  high 
a  viscosity  means  loss  of  power  in  overcoming  unnecessary  fluid 
friction. 

2.  Must  suit  the  Lubricating  system. 

When,  for  example,  the  oil  pipes  are  exposed  to  cold,  a  lower 
cold  test  oil  is  required  than  when  the  oil  pipes  are  not  so  exposed. 

3.  Must  be  of  such  a  nature  that  it  will  not  produce  deposits 
during  use,  exposed  to  the  influence  of  air,  gas,  water  or  impurities 
with  which  the  oil  may  come  into  more  or  less  intimate  contact 
while  performing  its  duty. 

The  particular  physical  and  chemical  tests  needed  will  depend 
on  the  class  of  work  for  which  the  oil  is  to  be  used,  and  will  be- 
come more  apparent  from  the  chapters  in  this  book  devoted  to 
particular  types  or  sections  of  engines  and  machinery. 

In  the  manufacture  of  lubricating  oils  it  is  of  the  greatest 
importance  that  the  various  grades  be  kept  always  as  closely  as 
possible  to  certain  predetermined  standards.  Engineers  who 
have  to  do  with  the  practical  application  of  oils  fully  appreciate 
this  point.  For  example,  a  drop  feed  lubricator  on  a  bearing  is 
set  to  give  a  certain  feed  of  oil  which  has  been  found  satisfactory; 
a  new  supply  of  oil  is  received  of  a  lower  or  higher  viscosity  than 
the  former  supply;  the  feed  of  the  lubricator  will  then  be  either 
greater,  which  means  oil  wasted,  or  smaller,  with  the  result  that 
the  bearing  may  run  warm. 

Physical  and  chemical  tests  of  lubricants  are  therefore  of  great 
value  to  the  oil  manufacturer  for  controlling  the  manufacture 
of  lubricating  oils  during  the  distillation,  refining  and  compound- 
ing operations,  up  to  the  point  when  the  oil  is  placed  in  the  stores 
ready  for  shipment,  Physical  and  chemical  tests  are  also  ex- 
tremely valuable  for  the  purpose  of  identifying  an  oil  or  for  de- 
tecting adulterations. 


TESTING  LUBRICANTS  35 

In  the  following  chapters  the  author  will  endeavor  to  show 
the  importance  of  physical,  chemical  and  mechanical  testing 
methods,  but  with  the  exception  of  one  or  two,  which  he  feels 
may  not  be  generally  known,  it  is  not  proposed  to  describe  the 
apparatus. 

The  author  has  divided  ''Testing  Lubricants"  into  two  sections, 
namely,  " Physical  and  Chemical  Tests"  and  " Mechanical 
Means  of  Testing  Lubricants, "  the  latter  section  dealing  briefly 
with  friction  testing  machines  and  works  methods  of  carrying 
out  comparative  tests  on  engines  and  machinery. 

PHYSICAL  AND  CHEMICAL  TESTS 

Physical  Tests 

Density  and  Specific  Gravity. 

Coefficient  of  Expansion. 

Flash  Point  and  Fire  Point. 

Volatility — Loss  by  Evaporation. 

Distillation. 

Specific  Heat. 

Cold  Test,  Pour  Test  and  Cloud  Test. 

Melting  Point. 

Color  and  Fluorescence. 

Viscosity  of  Oils. 

Viscosity  of  Semi-solid  Lubricants. 

Capillarity. 

Emulsification . 

Surface  Tension. 

Chemical  Tests 
Acidity. 

Oxidation  and  Gumming. 
Ash. 

Carbon  Residue. 
Asphalt  and  Tar. 
Oiliness. 
Impurities  (Dirt,  Glue,  Water). 

PHYSICAL   TESTS 

Density  and  Specific  Gravity. — The  specific  gravity  of  a  sub- 
stance is  the  weight  compared  with  that  of  an  equal  volume  of 
water  as  unity. 

In  the  United  States  and  Great  Britain  the  specific  gravity  is 
the  60°F./60°F.  value,  which  means  that  the  specific  gravity  is 
measured  at  60°F.  as  compared  with  water  at  60°F.  as  unity. 

On  the  Continent  the  15°C./4°C.  value  is  generally  used,  which 
means  that  the  specific  gravity  is  measured  at  15°C.  and  com- 
pared with  water  at  4°C.  as  unity,  this  being  the  temperature 
at  which  water  has  its  maximum  density. 


36  PRACTICE  OF  LUBRICATION 

Density  in  the  C.G.S.  system  (metric  system)  means  the 
weight  of  one  milliliter  ( =  cubic  centimeter)  of  a  substance  as 
compared  with  the  weight  of  one  milliliter  of  water  at  4°C.  The 
specific  gravity  15°C./4°C.  therefore  represents  in  the  metric 
system  the  density  of  the  substance  at  15°C.  The  15°C./4°C. 
specific  gravity  is  obviously  less  than  the  60°F./60°F.  value,  but 
as  the  coefficient  of  expansion  of  water  is  exceedingly  small,  the 
difference  in  value  is  only  slight. 

As  indicated  in  the  table,  p.  23,  the  specific  gravities  of  the 
various  fixed  oils  do  not  differ  much  from  one  another,  whereas 
the  specific  gravities  of  mineral  oils  differ  considerably,  depending 
not  only  upon  the  crude  itself,  but  also  upon  the  method  of  dis- 
tillation and  refining. 

For  oils  made  from  similar  crudes  by  similar  methods  the 
specific  gravity  increases  with  the  viscosity.  Speaking  generally, 
asphaltic  base  oils  and  Russian  oils  have  higher  specific  gravities 
than  paraffin  base  oils,  the  difference  for  similar  viscosity  oils 
being  from  0.020  to  0.040.  Oils  treated  by  acid  and  cracked  oils 
have  higher  specific  gravities  than  oils  treated  by  filtration  and 
uncracked  oils  respectively.  Coal  tar  oils  and  rosin  oils  have 
specific  gravities  in  the  neighborhood  of  1 .0,  coal  tar  oils  always 
being  above  1.0. 

The  specific  gravity  is  therefore  important,  since  when  coupled 
with  other  tests  it  assists  in  identifying  an  oil  as  coming  from  a 
certain  type  of  crude,  etc.  The  specific  gravity  has,  however, 
no  direct  bearing  on  the  lubricating  value  of  a  lubricant. 

The  specific  gravity  may  be  determined  by  pyknometer,  hydro- 
meter, or  the  Westphal  balance.  The  pyknometer  method  (spe- 
cific gravity  bottle  or  the  Sprengel  tube)  is  applicable  to  all 
liquids  and  is  the  most  accurate  method  for  lubricating  oils. 
The  hydrometer  and  the  Westphal  balance  are  less  accurate, 
but  both  methods  are  capable  of  giving  sufficiently  accurate 
results  for  commercial  purposes  and  are  handier  to  use  than  the 
pyknometer,  especially  the  hydrometer. 

The  Beaume  gravity  is  measured  by  a  hydrometer  and  is  much 
used  in  the  United  States.  The  conversion  of  gravity  from 
degrees  Beaume  to  specific  gravity  can  be  carried  out  according 
to  the  formula: 

Specific  Gravity  =  ^^ 

#£.-[-130 

The  conversion  table  No.  5  has  been  calculated  from  this  formula. 

As  one  litre  water  weighs  one  kilogram,  the  weight  of  one  litre 

oil  in  kilograms  is  expressed  by  its  specific  gravity.     As  one 


TESTING  LUBRICANTS 


37 


imperial  gallon  weighs  ten  pounds,  the  weight  of  one  imperial 
gallon  of  oil  in  pounds  is  equal  to  ten  times  its  specific  gravity. 
This  rule  cannot  be  applied  to  American  gallons,  one  American 
wine  gallon  equalling  five-sixth  imperial  gallon. 


TABLE  5. — TABLE  OP  60°F./60°F.  SPECIFIC  GRAVITIES 
(Corresponding  to  Each  Tenth  of  a  Degree  of  Beaume's  Hydrometer  Be- 
tween 15.0  and  50.0  Degrees  for  Liquids  Lighter  than  Water) 


15.  0-.  9655 

19.  0-.  9396 

23.  0-.  9150 

27.  0-.  8917 

3  1.0-'.  8605 

.1-.9649 

.1-.9389 

.1-.9144 

.1-.8912 

.1-.8690 

.2-.  9642 

.2-.  9383 

.2-.  9138 

.2-.  8906 

.2-.  8685 

.3-.  9635 

.3-.  9376 

.3-.  9132 

.3-.  8900 

.3-.  8680 

.4-.  9629 

.4-.  9370 

'  .4-.  9126 

.4-.  8894 

.4-.  8674 

.5-.  9622 

.5-.  9364 

.5-.  9120     .5-.  8889     .5-.  8669 

.6-.  9615 

.6-.  9358 

.6-.  9114 

.6-.  8883 

.6-.  8663 

.7-.  9609 

.7-.  9352 

.7-.  9109 

.7-.  8877 

.7-.  8658 

.8-.  9602 

.8-.  9346 

.8-.  9103 

.8-.  8871     .8-.  8652 

.9-.  9596 

.9-.  9340 

.9-.  9097 

.9-.  8866     .9-.  8647 

16.  0-.  9589 

20.  0-.  9333 

24.  0-.  9091 

28.  0-.  8861  1  32.  0-.  8642 

.1-.9582 

.1-.9327 

.1-.9085 

.1-.8855     .1-.8637 

.2-.  9576 

.2-.  9320 

.2-^9079 

.2-.  8849 

.2-.  8631 

.3-.  9569 

.3-.  9314 

.3-.  9073 

.3-.  8844 

.3-.  8626 

.4-.  9563 

.4-.  9308 

.4-.  9067 

.4-.  8838     .4-.  8621 

.5-.  9556 

.5-.  9302 

.5-.  9061 

.5-.  8833     .5-.  8615 

.6-.  9550 

,.6^3295 

.6-.  9055 

.6-.  8827     .6-.  8610 

.7-.  9543 

.7-.  9289 

.7-.  9049 

.7-.  8821     .7-.  8605 

.8-.  9537 

.8-.  9283 

.8-.  9044 

.8-.  8816     .8-.  8599 

.9-.  9530 

.9-.  9277 

.9-.  9038  !   .9-.  8810     .9-.  8594 

17.  0-.  9524 

21.  0-.  9271 

25.  0-.  9032 

29.  0-.  8805 

33.  ()-.  8589 

.1-.9517 

.1-.9265 

.1-.9027 

.1-.8800 

.1-.8584 

.2-.  9511 

.2-.  9259 

-  .2-.  9021 

.2-.  8794 

.2-.  8578 

.3-.  9504 

.3-.  9253 

.3-.  9015 

.3-.  8789 

.3-.  8573 

.4-.  9498 

.4-.  9247 

.4-.  9009 

.4-.  8783 

.4-.  8568 

.5-.  9492 

5-.  9241 

.5-.  9003 

.5-.  8777 

.5-.  8563 

.6-.  9485 

.6-.  9235 

.6-.  8997 

.6-.  8772 

.6-.  8557 

.7-.  9479 

.7-.  9229 

.7-.  8991 

.7-.  8766 

.7-.  8552 

.8-.  94  72 

.8-.  9223 

.8-.  8986 

.8-.  8760 

.8-.  8547 

,9-.  9466 

.9-.  9217 

.9-.  8980 

.9-.  8755 

.9-.  8542 

18.  0-.  9459 

22.  0-.  9210 

26.  0-.  8974 

30.  0-.  8750 

34.  0-.  8536 

.1-.9453 

.1-.9204 

.1-.8969 

.1-.8745 

.1-.8531 

.2-.  9447 

.2-.  91  98 

.2-.  8963 

.2-.  8739 

.2-.  8526 

.3-.  9440 

.3-.  9192 

.3-.  8957 

.3-.  8734 

.3-.  8521 

.4-.  9434 

.4-.  9186 

.4-.  8951 

.4-.  8728 

.   .4-.  8516 

.5-.  9428 

.5-.  9180 

.5-.  8946 

.5-.  8723 

.5-.  8511 

.6-.  9421 

.6-.  9174 

.6-.  8940 

.6-.  8717 

.6-.  8505 

.7-.  9415 

.7-.  9168 

.7-.  8934 

.7-.  8712 

.7-.  8500 

.8-.  9409 

.8-.  9162 

.8-.  8928 

.8-.  8706 

.8-.  8495 

.9-.  9402 

.9-.  91  56 

.9-.  8922 

.9-.  8701 

.9-.  8490 

38 


PRACTICE  OF  LUBRICATION 


TABLE  5 — (Continued) 


35.  0-.  8485 

39.  5-.  8259 

44.  0-.  8046 

48.  5-.  7843 

.1-.8480 

.6-.  8254 

.1-.8042 

.6-.  7839 

.2-.  8475 

.7-.  8249       .2-.  8037 

.7-.  7834 

.3-.  8469 

.8-.  8244        .3-.  8032 

.8-.  7830 

.4-.  8464 

.9-.  8240       .4-.  8027 

.9-.  7826 

.5-.  8459 

40.  0-.  8235       .5-.  8023 

49.  0-.  7821 

.6-.  8454        .1-.8230       .6-.  8019 

.1-.7817 

.7-.  8449 

.2-.  8226       .7-.  8014 

.2-.  7813 

.8-.  8444 

.3-.  8221 

.8-.  8009 

.3-.  7808 

.9-.  8439 

.4-.  8216 

.9-.  8005 

.4-.  7804 

"36.0-.8434 

.5-.  8211 

45.  0-.  8000 

.5-.  7799 

.1-8428 

.6-.  8206 

.1-.7996 

.6-.  7795 

.2-.  8423 

.7-.  8202 

..2-.  7991 

.7-.  7791 

.3-.  8418 

.8-.  8197 

.3-.  7986 

.8-.  7786 

.4-.  8413 

.9-.  8192 

.4-.  7982 

.9-.  7782 

.5-.  8408 

41.  0-.  8187 

.5-.  7977 

50.  0-.  7778 

.6-.  8403 

.1-.8183 

.6-.  7972 

.7-.  8398 

.2-.  8178 

.7-.  7968 

.8-.  8393 

.3-.  8173 

.8-.  7963 

.9-.  8388 

.4-.  8168 

.9-.  7959 

37.  0-.  8383 

.5-.  8163 

46.  0-.  7954 

.1-.8378 

.6-.  8158 

.1-.7950 

.2-.  8373 

.7-.  8153 

.2-.  7946 

.3-.  8368        .8-.  8149 

.3-.  7941 

.4-.  8363        .9-.  8144 

.4-.  7937 

.5-.  8358 

42.  0-.  8139 

.5-.  7932 

.6-.  8353 

.1-.8135 

.6-.  7928 

.7-.  8348 

.2-.  8130 

.7-.  7923 

.8-.  8343 

.3-.  8125 

.8-.  7918 

.9-.  8338 

.4-.  8120 

.9-.  7914 

38.  0-.  8333 

.5-.  8116 

47.  0-.  7910 

-.1-.8329 

.6-.  8111 

.1-.7905 

.2-.  8324 

.7-.  8106 

.2-.  7901 

.3-.  8319 

.8-.  8101        .3-.  7896 

.4-.  8314 

.9-.  8097 

.4-.  7891 

.5-.  8309 

43.  0-.  8092 

.5-.  7887 

.6-.  8301 

.1-.8088 

.6-.  7883 

.7-.  8299 

.2-.  8083 

.7-.  7878 

.8-.  8294 

.3-.  8078 

.8-.  7874 

.9-.  8289 

.4-.  8074 

.9-.  7869 

39.  0-.  8284 

.5-.  8069 

48.  0-.  7865 

.1-.8279 

.6  -.8065 

.1-.7860 

.2-.  8274 

.7-.  8060 

.2-.  7856 

.3-.  8269 

.8-.  8055 

.3-.  7852 

.4-.  8264 

.9-.  8050       .4-.  7847 

The  Twaddell  gravity  scale  is  sometimes  used  for  liquids 
heavier  than  water,  such  as  coal  tar  products,  caustic  potash, 


TESTING  LUBRICANTS 


39 


sulphuric  acid  and  other  chemicals.     To  convert  degrees  T wad- 
dell  to  specific  gravity  use  the  following  formula : 


Specific  Gravity 


1 000+5  X  degrees  Twaddell 


1000 


COEFFICIENT  OF  EXPANSION 

The  coefficient  of  expansion  is  the  expansion  or  contraction 
per  unit  volume  following  a  change  in  temperature  of  one  degree. 

The  coefficient  of  expansion  is  the  same  for  all  mineral  oils  of 
the  same  specific  gravity  and  can  be  taken  near  enough  for  prac- 
tical purposes  as  being:1 


Specific 
gravity 

Coefficient  of  expansion 

Per  °F. 

Per  °C. 

For  gasolene 

.620-.  760 
.780-.  830 

• 

.850-.  970 

.00050 

.00040 
.00036 

.00090 
.  00072 

.00065 

For  kerosene  
For  lubricating  oils,  including  fixed 
oils  

The  density  of  an  oil  will  vary,  with  a  certain  change  in  tem- 
perature, an  amount  equal  to  the  coefficient  of  expansion  mul- 
tiplied by  the  number  of  degrees  the  temperature  has  changed. 

To  know  the  value  of  the  coefficient  of  expansion  is  therefore 
useful  for  converting  the  gravity  measured  at  a  temperature 
different  from  the  standard  temperature  (which  is  60°F.  in  United 
Kingdom  and  United  States)  to  the  gravity  at  the  standard 
temperature.  Also  for  measuring  the  stock  of  oil  in  an  oil 
storage  tank,  as  the  volume  must  always  be  corrected  to  represent 
volume  at  a  standard  temperature. 

In  correcting  the  specific  gravity  for  variation  in  temperature, 
the  correction  coefficient  is  not,  as  is  often  assumed,  the  coefficient 
of  expansion,  but  the  product  of  the  latter  and  the  specific 
gravity  taken  at  the  temperature  of  the  oil.  It  may  be  useful 
to  show  how  the  true  correction  is  calculated. 

The  change  in  volume  due  to  change  of  temperature  is  ex- 
pressed in  the  fundamental  formula: 

VT   =  V60     [I  +  C(T  -  60)] 

Where      VT   =  Volume  of  a  certain  weight  of  oil  at  the  tem- 
perature T. 

F6o  =  Volume  of  the  same  weight  of  oil  at  60°F. 
C   =  Coefficient  of  expansion. 

1  U.  S.  A.  Bureau  of  Standard  Technologic  paper  No.  77:  Density  and 
Thermal  Expansion  of  American  Petroleum  Oils. 


40  PRACTICE  OF  LUBRICATION 

The  weight  of  the  oil  equals  the  volume  multiplied  by  the 
specific  gravity,  so  that: 

Feo  X  Seo  =  VT  X  ST;  or  VT  =  ^^          '     ,- 

where  £6o  and  ST  are  the  specific  gravities  of  the  oil  at  60°F.  and 
T°F.  respectively. 
We  can  now  rewrite  our  formula  as  follows : 

^60  *  S™  =  VGQ  [1  +  C  (T  -  60)]     or 

S6Q  =  ST  +  ST  X  C  X  (T  -  60) 

In  other  words,  the  specific  gravity  at  60°F.  equals  the  specific 
gravity  at  T°F.  plus  the  product  of  (1)  the  difference  in  tempera- 
ture between  T  and  60,  (2)  the  coefficient  of  expansion,  and  (3) 
the  specific  gravity  at  T°F. 

FLASH  POINT  AND  FIRE  POINT 

The  Flash  point  of  an  oil  is  the  temperature  at  which  the  oil 
gives  off  sufficient  vapors  to  ignite  momentarily  when  exposed 
to  a  flame  or  spark.  The  oil  must  be  heated  at  a  uniform  rate, 
and  not  too  rapidly,  as  that  would  give  too  low  a  flash  point. 

The  open  flash  point  is  the  flash  point  determined  when  heating 
the  oil  in  an  open  cup. 

The  closed  flash  point  is  the  flash  point  determined  when  heating 
the  oil  in  a  closed  vessel,  which  rather  prevents  the  vapors 
escaping,  so  that  the  closed  flash  point  is  always  lower  than  the 
open  flash  point.  The  difference  is  greater  the  higher  the  flash 
point  of  the  oil. 

The  fire  point  of  an  oil  is  the  temperature  at  which  the  oil  gives 
off  sufficient  vapors  to  ignite  and  continue  to  burn  when  ex- 
posed to  a  flame  or  spark.  The  test  is  made  with  the  same  appara- 
tus as  is  used  for  determining  the  flash  point,  the  oil  being  heated 
beyond  the  flash  point  until  the  fire  point  is  reached. 

No  oil  is  used  for  lubricating  purposes  with  an  open  flash  point 
less  than  300°F.  The  open  flash  points  of  all  lubricating  oils, 
including  fixed  oils  range  from  300°F.  to  650°F.  The  closed 
flash  point  of  a  lubricating  oil  is  recorded  only  for  special  oils, 
such  as  air  compressor  oils,  and  transformer  oils. 

The  apparatus  employed  for  testing  flash  and  fire  points  vary 
for  different  countries.  Thermometers  are  usually  standardized 
with  the  bulb  and  stem  at  the  same  temperature.  As  the  stem 
of  the  thermometer  when  determining  flash  and  fire  points  is  not 
exposed  to  high  temperature,  the  results  should  be  corrected  by 
adding  to  the  thermometer  readings  the  following  degrees  F. 


TESTING  LUBRICANTS  41 

275—300—  5  425—450—13 

300—325—  6  450—500—16 

325—350—  7  500—550—20 

350—375—  8  550—600—23 

375—400—10  600—650—27 

400— 425— 1 1  650—700—30 

Pensky-Martens  apparatus  is  more  widely  used  for  lubricating 
oils  in  many  countries  than  any  other  apparatus. 

The  Gray  instrument  is  an  adaptation  of  the  Pensky-Martens 
apparatus,  and  the  two  instruments  give  identical  readings. 

The  Abel  instrument  is  principally  used  for  taking  closed  flash 
points  of  spirits  and  illuminating  oils. 

Fixed  oils  do  not  evaporate  until  they  begin  to  decompose, 
whereas  mineral  oils  commence  to  evaporate  long  before  their 
flash  points  are  reached.  When  fixed  oils  are  heated  sufficiently 
to  give  off  vapors,  destructive  distillation  has  already  com- 
menced, and  it  will  be  seen  from  Table  No.  3  page  23  that  the  flash 
points  of  fixed  oils  are  much  higher  than  for  mineral  oils  of  similar 
viscosities,  the  open  flash  points  ranging  from  460°F.  to  630°F. 

The  difference  between  the  open  flash  point  and  the  fire  point 
of  lubricating  oils  is  approximately  as  follows: 

Difference  between  open  flash 
point  and  fire  point, °F. 

1.  Straight  mineral  distilled  lubricating  oils .  40    to    55 

2.  Cylinder  oils  (undistilled) 50    to     75 

3.  Mixtures   of  mineral   distilled   oils   with 

cylinder  oils  or  fixed  oils 40     to     75 

The  evaporation  point  is  the  temperature  at  which  an  oil  begins 
to  give  off  vapors;  this  temperature  is  normally  about  150°F. 
to  180°F.  lower  than  the  flash  point,  but  is  so  difficult  to  deter- 
mine accurately,  and  depends  so  much  on  the  human  element, 
that  its'  determination  is  of  no  practical  importance. 

VOLATILITY— LOSS  BY  EVAPORATION 

Oil  exposed  to  a  high  temperature  for  a  certain  number  of 
hours  loses  a  certain  amount  in  weight,  which  is  called  "loss  by 
evaporation." 

The  oil  is  usually  heated  in  an  open  beaker,  and  experience 
shows  that  the  loss  by  evaporation  is  greatly  influenced  by  the 
size  and  shape  of  the  beaker,  the  amount  of  oil  used,  air  currents, 
etc.  When  giving  figures  for  loss  by  evaporation,  one  should 
therefore  state*  all  such  particulars  for  the  test  to  be  of  any 
value  at  all. 

The  evaporation  test  is  seldom  of  any  great  value;  if  a  lubri- 


42  PRACTICE  OF  LUBRICATION 

eating  oil  has  an  open  flash  point  above  300°F.  the  loss  by  evapo- 
ration will  usually  be  of  no  importance;  the  flash  point  will 
prove  a  safe  guide  as  to  whether  the  oil  contains  light  petro- 
leum fractions  of  a  kerosene  or  gasolene  nature. 

Where  oils  are  known  to  be  contaminated  with  low  flash  pro- 
ducts, the  evaporation  test  can  be  used  to  determine  the  percen- 
tage present  of  these  products,  as  for  example  with  used  oils  from 
the  crank  case  of  petrol  or  oil  engines. 

Lubricating  oils  used  for  high  vacuum  pumps  (in  the  manufac- 
ture of  electric  bulbs)  must  have  a  low  volatility  in  vacuum  and 
should  have  their  vapor  tension  tested,  when  exposed  to  vacuum 
and  at  a  temperature  approximating  the  working  temperature. 

Transformer  oils  are  often  subjected  to  the  evaporation  test, 
as  many  of  these  oils  are  low  flash  oils  (occasionally  flashing  be- 
low 300°F.)  and  the  loss  by  evaporation  during  use  may  easily 
become  an  important  feature. 

Air  compressor  oils  are  sometimes  tested  with  advantage  for 
evaporation  losses,  particularly  when  the  compressed  air  is  used 
for  tunnel  work  or  for  operating  tools  or  engines  in  confined 
spaces,  or  in  underground  mines,  as  the  presence  of  an  apprecia- 
ble amount  of  oil  vapor  in  the  compressed  air  will  affect  the 
eyes  and  throats  of  the  workers. 

Archbutt  has  designed  a  simple  vaporimeter, l  in  which  the  oil 
is  placed  in  a  boat  inside  a  %  inch  internal  diameter  tube,  through 
which  is  passed  hot  air  or  steam,  the  whole  heated  to  the  desired 
temperature  by  means  of  a  gas  burner.  The  apparatus  appears 
to  give  very  consistent  results  and  to  lend  itself  well  to  standar- 
dization. 

The  vessels  used  for  evaporation  tests  should  be  porcelain  or 
glass;  metal  vessels  have  a  catalytic  effect,  which  influences  the 
results. 

From  tests  carried  out  by  Archbutt  and  others,  it  is  evident 
that  no  simple  relation  (if  any  relation  at  all)  exists  between  the 
volatility  of  an  oil  and  its  flash  point. 

.  Distillation.  In  rare  cases  lubricating  oils  are  subjected  to  dis- 
tillation tests  with  a  view  to  finding  out  the  percentages  of  low 
viscosity,  medium  viscosity,  and  high  viscosity  oils  of  which  they 
are  composed. 

All  lubricating  oils  are  mixtures  of  hydrocarbons  having  differ- 
ent viscosities  and  while  it  is  not  of  any  considerable  interest  to 
further  analyze  from  a  distillation  point  of  view  the  eight  main 
types  of  oils  referred  to  on  page  11,  yet  it  may  be  of  interest  to 
find  out  whether  a  certain  lubricating  oil  is  a  mixture  of  cylinder 
'  Archbutt  &  Deeley;  Imbrication  and  Lubricants,  page  215. 


TESTING  LUBRICANTS  43 

stock  and  a  lower  viscosity  distilled  lubricating  oil,  and  in  that 
case  what  the  percentage  of  cylinder  stock  amounts  to. 

An  interesting  series  of  distillation  tests  were  carried  out  by 
J.G.  O'Neill,  Chemist,  U.S.  Naval  Experiment  Station,  Minnea- 
polis, published  in  the  May  1916  Journal  of  the  American  Society 
of  Naval  Engineers.  Mr.  O'Neill  distills  the  oil  by  means  of 
superheated  steam,  but  does  not  employ  a  vacuum.  By  dis- 
tilling a  number  of  oils  into  their  various  fractions  and  further 
analysing  these  fractions,  he  brings  out  the  typical  characteristics 
of  asphaltic  base  and  paraffin  base  oils. 

Other  experimenters  distill  the  oils  under  a  high  vacuum  which, 
however,  is  rather  a  delicate  test  to  carry  out  in  the  laboratory 
and  more  complicated  than  distilling  without  the  use  of  vacuum. 
There  is,  however,  no  standard  method  adopted  for  a  distillation 
test  of  lubricating  oils,  nor  does  this  test  seem  to  be  of  particular 
interest  to  ordinary  consumers.  On  the  other  hand,  it  may  be  of 
considerable  interest  to  oil  refineries  or  lubricating  oil  companies 
with  a  view  to  finding  out  the  characteristics  and  component  parts 
of  competitive  products. 

Specific  Heat.  The  specific  heat  of  a  lubricating  oil  means  the 
amount  of  heat  required  to  raise  the  temperature  of  1  Ib.  of  oil 
1°F.,  or  1  kilo  of  oil  1°C.,  as  compared  with  the  amount  of  heat 
required  to  heat  1  Ib.  of  water  1°F.  or  1  kilo,  of  water  1°C., 
respectively.  The  specific  heat  of  water  is  therefore  1 .00. 

A  considerable  amount  of  work  in  connection  with  specific 
heats  of  oils  has  been  done  by  Prof.  Charles  F.  Mabery  (Proceed- 
ings of  the  American  Academy  of  Arts  &  Sciences,  Volume  37 
page  20,  March  1902).  Prof.  Mabery  has  shown  that  the  specific 
heats  of  the  paraffin  series  of  hydrocarbons  are  higher  than  the 
specific  heats  of  the  naphthenes,  defines,  and  other  hydrocarbons 
less  rich  in  hydrogen  than  the  paraffins. 

The  specific  heat  is  higher  for  the  lower  viscosity  oils  than  for 
those  of  higher  viscosity,  although  the  difference  amounts  only 
to  a,  few  per  cent.  The  specific  heat  also  increases  slightly 
with  increasing  temperatures. 

For  practical  purposes,  however,  the  specific  heat  may  be  taken 
as  follows: 


Character  of 
hydrocarbons 

Specific  heat 
@  50°C, 

Paraffin  base  distilled  low  viscosity  oils  
Russian   oils   and   heavy   viscosity   Pennsyl- 
vanian  oils  etc 

Cn.H2n  +  2 
Cn  H2n 

.49 
.47 

Manv  asphaltic  base  oils 

Cn.H2n  -  2 

.44 

44  PRACTICE  OF  LUBRICATION 

The  above  values  for  specific  heat  show  a  characteristic  dif- 
ference between  the  different  lubricating  oils,  which  is  of  some 
importance  in  connection  with  lubrication,  as  the  frictional  heat 
developed  during  the  operation  of  machinery  heats  the  oil  film, 
thus  reducing  its  viscosity.  The  lower  the  specific  heat  the 
greater  will  be  the  temperature  rise  of  the  oil  in  the  film  and  there- 
fore the  greater  will  be  the  reduction  of  viscosity.  If  abnormal 
heating  takes  place,  oils  having  a  low  specific  heat  will  quickly 
thin  out,  the  practical  result  of  this  being  that  such  oils  offer  less 
security  under  severe  conditions  than  oils  having  a  high  specific 
heat. 


COLD  TEST,  POUR  TEST  AND  CLOUD  TEST 

When  lubricating  oils  are  cooled  they  do  not  congeal  suddenly, 
as  does  for  example  water  when  it  turns  into  ice,  but  being  mix- 
tures of  products  of  different  nature,  they  gradually  become 
more  and  more  viscous  until  they  finally  set  solid;  the  temper- 
ature at  which  they  congeal  is  called  the  setting  point,  or  cold 
test. 

The  lowest  temperature  at  which  the  oil  will  flow  or  pour  out  of 
a  receptacle,  is  usually  taken  as  being  5°F.  above  the  setting 
point  and  is  called  the  pour  test. 

The  temperature  at  which  the  oil  commences  to  become  cloudy- 
paraffin  wax  separating  out — is  called  the  cloud  test,  but  it  is  diffi- 
cult to  determine  this  temperature  with  accuracy  and  the  cloud 
test  is  nowadays  rarely  spoken  of  in  connection  with  lubricating 
oils. 

Stirring.— When  the  setting  point  of  mineral  oils  is  being 
determined,  the  oil  must  not  be  stirred,  as  by  stirring  the  network 
of  solid  hydrocarbons  is  broken  up  and  the  setting  point  will 
be  from  5°F.  to  10°F.  lower  than  when  the  oil  is  cooled  without 
stirring.  Archbutt,  however,  recommends  stirring  when  testing 
fixed  oils. 

Russian  oils,  Californian  and  other  non-paraffinic  base  oils, 
have  no  "cloud  test,"  as  they  contain  no  solid  paraffin;  their 
setting  points  are  therefore  lower — from  20°F.  to  40°F.  lower 
than  those  of  paraffin  base  oils. 

Sometimes  heavy  viscosity  paraffin  base  oils  become  chilled 
during  transit  in  cold  weather,  as  a  result  the  amorphous  wax 
commences  to  solidify  in  oily  lumps  throughout  the  body  of  the 
oil.  The  oil  will  therefore  be  much  thicker  than  its  standard 
(real)  viscosity  and  will  not  be  homogeneous.  To  bring  the 
oil  back  to  its  normal  viscosity,  it  is  necessary  to  heat  it  suf- 


TESTING  LUBRICANTS  45 

ficiently  to  melt  the  paraffin  wax,  say  to  160°F.  or  170°F.,  the 
melting  points  of  paraffin  wax  ranging  from  100°F.  to  130°F. 

When  light  viscosity  lubricating  oils,  become  chilled,  some  of 
the  paraffin  wax  sometimes  crystallizes  out  in  the  form  of  shiny 
needles  floating  in  the  oil;  they  will  only  dissolve  in  the  oil 
if  heated  to  a  temperature  above  their  melting  point. 

Heating. — When  testing  the  setting  point  of  oils  containing 
paraffin  wax  they  should  for  the  reasons  just  given  always  be 
previously  heated  to  a  temperature  of  160-170°F. 

Cooling. — The  oil  should  be  cooled  slowly,  as  rapid  cooling 
means  that  the  setting  point,  as  determined,  will  be  too  low. 
This  is  particularly  important  for  fixed  oils.  The  test  tube 
or  bottle  containing  the  oil  should  therefore  be  placed  inside 
another  tube  %"  larger  in  diameter,  the  air  space  between 
the  tubes  preventing  too  rapid  cooling. 

Apparatus. — There  is  a  variety  of  apparatus  employed  for 
testing  the  setting  point,  pour  test  and  cloud  test  of  oils.  Some 
aim  at  determining  the  setting  point,  as  the  temperature  at  which 
the  oil  in  the  vicinity  of  the  thermometer  ceases  to  flow,  when  the 
vessel  or  tube  is  tilted  for  ten  minutes.  Others  aim  at  determin- 
ing the  pour  test,  as  the  temperature  at  which  a  definite  quantity 
of  the  oil  will  just  flow  from  end  to  end  of  a  test  tube  of  definite 
dimensions  when  placed  horizontally  or  inverted;  this  method 
is  largely  used  for  cylinder  oils  and  black  oils. 

The  determinations  of  setting  point  or  pour  test  are  usually 
accurate  within  5°F. 

Cooling  Mixtures — For  oils  congealing  above  35°F.  pounded 
ice  is  used.  For  oils  congealing  at  from  35°F.  to  —  5°F.  a  mixture 
of  snow  or  pounded  ice  and  salt  is  used,  the  salt  preferably  being 
added  gradually  to  bring  down  the  temperature  5°F.  at  the  time. 

For  oils  congealing  below  zero,  solid  carbon  dioxide  can  be 
used  or  calcium  chloride  (crystals)  and  ice  (  —  40°F.),  or  solid 
carbon  dioxide  may  be  added  to  dry  acetone,  by  which  a  tem- 
perature as  low  as  —  70°F.  can  be  obtained. 

The  setting  point  of  an  oil  must  be  low  enough  so  that  the 
oil  will  flow  readily  under  working  conditions  and  that  a  sufficient 
amount  will  reach  the  bearings  or  parts  to  be  lubricated.  Many 
mishaps  have  been  caused  by  the  oil  solidifying  in  the  lubricators 
or  refusing  to  run  through  exposed  oil  pipes  to  the  bearings. 
While,  therefore,  in  tropical  or  warm  climates  the  setting  point 
of  lubricating  oils  ordinarily  is  of  no  importance,  this  feature  is 
certainly  important  in  temperate  climates  and  particularly 
so  in  colder  climates  like  Canada,  Northern  Scandinavia,  northern 
Russia,  etc. 


46  PRACTICE  OF  LUBRICATION 

Oils  used  for  refrigerating  machines  and  other  special  machines 
must  always  have  low  setting  points,  independent  of  the  climatic 
conditions.  Low  setting  point  must  be  given  special  considera- 
tion in  connection  with  engines  or  machinery  operating  in  the 
open,  such  as  railway  rolling  stock,  certain  machinery  in  mines 
and  quarries,  aeroplanes,  automobiles,  etc.,  etc.  Oils  used  for 
engines  or  machinery  operating  inside  buildings  do  not  require 
the  same  consideration  as  regards  setting  point. 

Whenever  low  setting  point  oils  are  required,  the  winter  con- 
ditions are  of  course  more  severe  than  summer  conditions, 
and  so  frequently  two  sets  of  oils  are  used,  for  summer  and 
winter  use  respectively. 

MELTING  POINT 

The  melting  point  of  an  oil,  fluid  at  ordinary  temperatures,  is 
the  same  as  its  setting  point,  or  rather  its  pour  test;  in  fact,  the 
latter  is  sometimes  determined  by  freezing  the  oil  solid,  then 
allowing  it  to  melt  exposed  to  the  room  temperature,  under 
continuous  stirring,  until  the  oil  commences  to  pour.  The 
melting  point  of  fats,  lubricating  greases  or  oils,  non-fluid  at 
ordinary  temperatures  is  not  a  definite  temperature,  as  they 
become  soft  and  gradually  melt,  when  heated. 

Melting  points  of  fats  and  greases  may  be  determined  in 
several  ways,  as  described  by  Archbutt1;  no  uniform  system 
has  been  agreed  upon,  and  there  are  great  discrepancies  between 
the  results  when  different  apparatus  is  used  and  by  different 
observers. 

Low  melting  point  greases  (M.P.  40°C.  to  50°C.)  are  required 
for  railway  axle  box  lubrication.  Medium  melting  point  greases 
are  used  for  general  lubrication,  such  as  cup  greases  or  solidified 
oils  (M.P.  75°C.  to  95°C.).  High  melting  point  greases  are 
used  for  high  temperature  bearings  for  rotary  cement  kilns, 
dryer-journals  and  callendar  journals  on  paper  machines,  Beeter 
bearings,  etc.  (M.  P.  150°C.  to  250°C.). 

COLOR  AND  FLUORESCENCE 

Fixed  oils  are  transparent  and  either  almost  colorless  or 
slightly  yellow  or  greenish-yellow  in  transmittent  light. 

Distilled  mineral  oils  are  transparent  and  range  in  color  from 
water  white,  through  yellow,  to  deepest  red  in  transmittent 
light. 

1  A.  &  D.  L.  and  L.,  pages  223-229. 


TESTING  LUBRICANTS  47 

Undistilled  mineral  oils — cylinder  stocks — are  very  dark  in 
color;  dark  cylinder  stocks  range  from  dark  brownish  red  to 
black,  whereas  the  filtered  cylinder  stocks  are  lighter  in  color 
and  range  from  deep  red  to  deepest  red  in  transmittent  light. 

Lovibond's  tintometer  may  be  used  to  determine  by  com- 
parison with  standard  colors  the  color  of  oil  in  a  1-inch  cell. 
The  darker  the  oil  the  higher  is  the  color  number.  If  determined 
in  a  cell  of  different  thickness  the  thickness  of  the  cell  should  be 
stated,  so  that  the  color  number  may  be  calculated  in  terms  of 
a  1-inch  cell. 

Wearham  has  designed  an  apparatus  which  gives  the  color  of 
an  oil  or  any  other  material,  liquid  or  solid,  in  terms  of  percent- 
ages of  primary  red,  blue  and  yellow.  The  color  determined 
in  this  manner  is  definitely  expressed  and  can  be  reproduced 
in  the  apparatus  to  act  as  a  standard  for  matching  colors  at  the 
refineries  or  oil  blending  works. 

The  color  of  an  oil  in  reflected  light  is  called  "bloom"  or 
fluorescence. 

Paraffin  base  oils  have  a  greenish  bloom;  Russian  and  many 
asphaltic  base  oils  have  a  bluish  bloom.  Dark  cylinder  stocks 
are  dark  brown  or  black,  whereas  highly  filtered  cylinder  stocks 
show  the  fluorescence  clearly,  and  are  usually  green,  being  pro- 
duced from  paraffin  base  crudes. 

Oils  which  during  use  have  been  oxidized  (turbine  oils,  crank- 
case  oils,  etc.)  almost  immediately  change  their  bloom  and  assume 
a  brownish  color  in  reflected  light.  Oils  which  contain  mois- 
ture become  cloudy  or  even  opaque  and  appear  to  be  darker  in 
color  than  when  dry. 

Oils  are  made  paler  by  filtration,  so  that  neutral  oils  are  rather 
pale,  although  usually  not  so  pale  as  the  acid  treated  pale  oils. 

Pale  oils  are  more  easily  produced  from  Russian  crude,  Cali- 
fornian,  Texas  and  similar  crudes. 

The  coloring  matter  in  paraffin  base  oils  is  only  removed  with 
difficulty;  hence  white  transformer  oils  and  white  medicinal 
oils  are  usually  made  from  non-paraffinic  base  crudes,  Russian 
crudes  in  particular. 

Coloring  matter  in  oil  consists  of  very  complex  unsaturated 
hydrocarbons,  which  easily  decompose  under  heat  or  when 
exposed  to  oxidation.  Dark  red  oils  when  used  for  internal 
combustion  engines  or  air  compressors  therefore  produce  more 
carbon  than  pale  oils,  and  dark  colored  circulation  oils  are 
more  inclined  to  produce  deposits  in  steam  turbines  and  enclosed 
type  steam  engines  than  pale  oils.  Similarly,  dark  cylinder  oils 
produce  more  carbon  than  filtered  cylinder  oils  when  used  for 
steam  engines  employing  superheated  steam. 


48  PRACTICE  OF  LUBRICATION 

Where  oils  are  not  exposed  to  great  heat  or  oxidation,  it  is 
immaterial  whether  they  are  lighter  or  darker  in  color. 

VISCOSITY 

The  viscosity  of  an  oil  is  a  measure  of  its  resistance  to  flow- 
its  internal  friction — and  is  inversely  proportional  to  its  fluidity. 
A  viscous  or  high  viscosity  oil  is  "  thick"  and  flows  with  difficulty; 
a  low  viscosity  oil  is  "thin"  and  flows  readily. 

The  most  accurate  method  of  determining  viscosity  which  is 
chiefly  used  in  science  is  that  of  Poiseuille,  by  measuring  the 
rate  of  flow  of  the  oil  through  a  capillary  tube  (a  very  narrow 
tube)  under  known  conditions  of  temperature  and  pressure. 

For  commercial  purposes  the  viscosity  is  usually  determined  by 
measuring  the  time  taken  in  seconds  for  a  certain  volume  of  oil 
to  flow  out  through  a.  short  vertical  tube  of  standard  dimensions. 

Poiseuille's  Method. — PoiseuihVs  method  is  based  upon  two 
facts,  which  he  proved  experimentally: 

1.  That  the  rate  of  flow  of  liquid  through  a  capillary  tube  of 
suitable  dimensions  is  proportional  to  the  pressure  and  inversely 
proportional  to  the  length  of  the  tube. 

2.  That  the  rate  of  flow  through  a  capillary  tube  of  cylindrical 
bore  is  proportional  to  the  fourth  power  of  the  radius  of  the  bore. 

The  viscosity  of  the  fluid  in  absolute  measure  is  then  given 
approximately  by: 

Absolute  Viscosity  =  rj  =  -7^7-* 

&Va 

in  which  "g"  is  the  acceleration  due  to  gravity,  "d"  the  density 
of  the  liquid,  "h"  the  mean  head,  "r"  the  radius  of  the  bore 
of  the  capillary  tube  in  centimetres,  "t"  the  time  in  seconds, 
"v"  the  volume  of  liquid  discharged  in  cubic  centimetres,  and 
"a"  the  length  of  the  tube  in  centimetres. 

Prof,  Reynolds  has  shown  that  Poiseuilles  formula  is  substan- 
tially correct  when  r-  -  is  less  than  700  where  "v"  is  the  mean 
velocity  of  the  fluid. 

To  obtain  the  true  viscosity,  corrections  must  be  made : 

1.  For  the  viscous  resistance  to  the  flow  of  the  liquid  at  the 
ends  of  the  tube. 

2.  For  the  abnormal  flow  of  the  liquid  on  first  entering  the  tube. 

3.  For  the  kinetic  energy  with  which  the  liquid  leaves  the  tube. 

4.  For  the  resistance  due  to  surface  tension  effects  at  the  dis- 
charge orifice. 

Corrections  (1)  and  (2)  have  not  yet  been  devised  but  errors 
due  to  these  effects  may  be  reduced  to  very  small  proportions 


TESTING  LUBRICANTS 


49 


by  making  the  tube  long.     Correction  (3)  is  made  by  deducting 

v2 
from  the  mean  head  a  quantity     ;  this  correction  maybe  made 

y 

very  small  by  using  a  tube  so  narrow  and  so  long  that  the  move- 
ment of  the  liquid  is  very  slow.  The  error  due  to  surface  tension 
effects  which  may  be  serious  is  so  variable  that  correction  (4)  is 
best  eliminated  altogether  by  immersing  the  discharge  orifice 
in  the  liquid  and  making  a  suitable  deduction  from  the  head. 

In  the  absolute  viscometer  used  by  Archbutt  and  Deeley  a 
capillary  tube  0.6180  mm.  diameter  and  21.991  cm.  long  was 
employed.  The  absolute  viscosity  of  water 
at  20°C.  determined  by  this  apparatus  was 
0.0102$  dyne  per  sq.  cm.,  which  agrees  well 
with  results  by  other  experimenters. 

The  absolute  viscosity  of  a  liquid  may  be 
defined  as :  "  The  force  which  will  move  a  unit 
area  of  plane  surface  with  unit  speed  relative 
to  another  plane  surface  from  which  it  is 
separated  by  a  layer  of  the  liquid  of  unit 
thickness." 

The  absolute  viscosity  is  therefore  correctly 
expressed  in  dynes-second  per  sq.  cm.  but  is 
usually  referred  to  as  dynes  per  sq.  cm. 

The  term  "Poise"  has  been  coined  from  the 
name  of  Poiseulle  and  signifies  "one  dyne- 
second  per  sq.  cm."  As  an  absolute  viscosity 
of  1  Poise  means  a  fairly  viscous  oil,  the 
term  "Centipoise"  is  used,  representing  one- 
hundredth  of  a  poise,  the  same  as  one  centi- 
metre equals  one-hundredth  part  of  a  metre. 

Ostwald's  viscometer,  Fig.  1,  is  capable  of 
giving  the  true  relative  viscosity  in  terms  of  the  viscosity  of  water 
or  other  standard  liquid,  which  is  called  the  specific  viscosity, 
when  .compared  with  the  viscosity  of  water  at  20°C.  as  unit. 
It  consists  of  a  glass  U-tube,  one  limb  of  which  is  a  capillary 
tube  from  a  to  b.  A  known  volume  of  oil  is  introduced  into 
the  wide  limb  at  c,  and  sucked  up  at  d,  until  the  level  is  above  e. 
The  time  occupied  in  flowing  back  through  the  capillary  ab 
whilst  the  level  falls  from  e  to  a  is  noted. 

If  t.d  and  t\.d\  are  the  time  of  flow  and  density  of  the  liquid  and 
water  respectively,  and  if  the  viscosity  of  water  is  taken  as  unity, 
then  the 

Specific  Viscosity  =  -'—T 


FIG,        1.— Ostwulds 
viscometer. 


50 


PRACTICE  OF  LUBRICATION 


Commercial  Viscometers.— The  most  widely  used  instruments 
are  Saybolt  (United  States) ,  Redwood  (Great  Britain)  and  Engler 
(Continent). 

The  standard  dimensions  of  outflow  tubes,  etc.,  are  as  follows: 


Efflux  Tube  Dimensions 

Volume  of  oil 
discharged 

Oil  charges 

Saybolt  
Redwood 

13  mm.  X  1.8  mm. 
10  mm.  X  1.5  mm. 

60 
50 

70 
130 

Encrler 

20mm.  X  {  ™  mm-  ?* 

200 

240 

1  2.8  mm.  bottom 

These  instruments  are  described  in  greater  detail  in  most 
standard  handbooks. 

The  viscosities  for  Saybolt  and  Redwood  are  given  in  seconds, 
whereas  with  the  Engler  instrument,  the  Engler  number  equals 
the  outflow  in  seconds  divided  by  the  efflux  time  of  water  at  20° 
C.,  which  is  50"-52",  varying  slightly  for  different  instruments. 
The  Engler  number  is  therefore  a  kind  of  specific  viscosity  and 
can  be  converted  into  absolute  viscosity  by  the  formula,  page  51. 

All  three  viscometers  have  efflux  tubes  so  large  and  compara- 
tively short  that  a  large  proportion  of  the  energy  of  flow,  particu- 
larly for  low  viscosity  liquids,  is  carried  away  in  the  issuing  stream 
of  liquid  and  not  used  for  overcoming  the  fluid  friction  inside  the 
efflux  tube.  For  example,  with  the  Engler  viscometer  the  per- 
centage of  energy  used  in  overcoming  fluid  resistance  within  the 
efflux  tube  is  95  per  cent,  or  more  in  the  case  of  a  heavy  viscosity 
oil,  whereas  with  water  it  is  only  about  12  per  cent. 

The  relation  between  the  absolute  viscosity  of  an  oil  and  its 
kinematic  viscosity,  as  measured  by  Saybolt,  Redwood  or  Engler 
viscometers,  is  fairly  uniform  for  medium  or  heavy  viscosity 
oils,  but  when  the  kinematic  viscosity  is  lower  than  say  100" 
Saybolt,  the  absolute  viscosity  falls  away  more  rapidily  than  the 
corresponding  kinematic  viscosity  figures.  W.  H.  Herschell1  and 
W.  F.  Higgins2  give  formulae  for  calculating  the  absolute  viscosity 
at  a  certain  temperature  when  the  specific  gravity  and  kinematic 
viscosity  are  known  for  this  same  temperature. 

In  the  following  formulae : 

"Specific  Gravity"  means  the  specific  gravity  value  as  com- 
pared with  water  at  60°F. 

1  U.  S.  Department  of  Commerce,  Technological  Paper  No.  100. 
;  "On  Methods  and  Apparatus  for  Petroleum  Testing,"  National  Physical 
Laboratory,  Collected  Researches. 


TESTING  LUBRICANTS  51 

"Saybolt"    means    Saybolt    Viscosity   measured    in  seconds. 

"Engler"  means  Engler  efflux  time,  measured  in  seconds,  not 
the  Engler  number.  (The  Engler  apparatus  employed  gave  an 
efflux  time  of  50.3  sees,  for  water  at  20°C.) 

"  Redwood"  means  Redwood  Viscosity,  50  c.c.  test,  measured 
in  seconds. 

The  figures  for  absolute  viscosity,  specific  gravity,  and  kine- 
matic viscosity  are  corresponding  values  at  the  same  temperature. 
Absolute  Viscosity  =  Specific  Gravity  (0.00213  Saybolt- 

1.535  \ 

-  ).      (Herschell) 
Saybolt/ 

Absolute  Viscosity  =  Specific  Gravity  (0.00147  Engler- 

(Herschell) 


Engler 

Absolute  Viscosity  =  Specific  Gravity  (0.00260  Redwood- 

1.715    \ 

-)•     (Higgms) 
Redwood/ 

Workshop  Viscometers.  —  Various  rough  and  ready  methods 
have  been  suggested  for  comparing  the  viscosity  of  two  oils  or 
for  approximate  determination  of  viscosity,  such  as  allowing  a 
drop  of  oil  to.  run  down  an  incline,  counting  the  number  of  drops 
falling  from  a  pipette  in  a  given  time,  watching  the  rate  at  which, 
when  a  narrow  test  tube  is  almost  filled  with  oil  and  inverted,  the 
air  bubble  travels  up  through  the  oil,  etc.  All  these  methods  are 
inaccurate  and  there  are  so  many  influencing  factors  that  the 
results  are  apt  to  be  very  misleading. 

The  only  attempt  at  solving  this  problem  that  appears  to  be  of 
promise  is  the  viscometer  designed  and  patented  by  Michell, 
the  inventor  of  the  "  Michell  bearing."  The  viscometer  is 
illustrated  in  Fig.  2  and  consists  of  a  cup  (1)  into  which  fits  a 
steel  ball  (2)  ;  an  oil  film  is  interposed  between  the  two,  its  thick- 
ness being  determined  by  the  three  raised  spots  (3)  which  in  one 
of  the  instruments  protrude  0.001  of  an  inch  beyond  the  cup  sur- 
face. The  handle  (4)  is  hollow  to  receive  a  thermometer  for 
registering  the  temperature  of  the  cup. 

There  is  a  groove  (5)  in  the  cup  which  holds  a  supply  of  oil  by 
capillary  attraction.  When  the  ball  is  suspended  the  relatively 
large  amount  of  oil  retained  in  the  groove  is  drawn  upon  to  feed 
the  film  between  the  ball  and  the  cup,  until  the  film  breaks  and 
the  ball  drops. 


'52 


PRACTICE  OF  LUBRICATION 


The  author  has  made  a  few  experiments  with  this  viscometer 
and  used  it  in  the  following  two  manners: 

1  A  few  drops  of  oil  were  placed  in  the  cup,  the  ball  inserted  and  the  two 
pressed  together  until  the  ball  was  felt  to  grip.     The  instrument  was  then 
inverted,  the  time  for  the  ball  to  drop  was  recorded  in  seconds  and  also  the 
temperature  of  the  cup. 

2  Both  the  ball  and  cup  were  immersed  in  a  sufficient  amount  ot  oil  to 
cover  them,  the  whole  being  heated  to  the  required  temperature  and  that 
temperature  being  maintained  for  15  minutes.     The  ball  was  then  pressed 
into  the  cup,  the  instrument  lifted  out-  of  the  oil  and  the  time  required  for 
the  hall  to  drop  was  recorded. 


FIG.  2. — Michell's  workshop  viscometer. 


The  first  method  is  very  convenient  for  workshop  use,  but  the 
viscosity  readings  may  easily  err  as  much  as  ±  25  per  cent,  from 
the  true  viscosity  on  account  of  the  uncertainty  of  the  oil  film 
temperature  being  correctly  recorded.  The  second  method  is 
slightly  more  elaborate,  but  is  capable  of  giving  results  which  are 
almost  as  accurate  as  the  usual  commercial  viscometers. 

Each  Michell  instrument  is  marked  with  a  conversion  factor, 
which  multiplied  by  the  time  in  seconds  taken  for  the  ball  to 
drop  gives  the  absolute  viscosity  of  the  oil. 

Using  the  Michell  viscometer  with  reasonable  care,  the  author 
found  that  the  average  of  ten  consecutive  readings  obtained  by 
the  immersion  method  and  the  viscosity  obtained  by  a  Redwood 


TESTING  LUBRICANTS 


53 


viscometer  (when  converting  the  latter  readings  into  absolute 
viscosities)  never  differed  more  than  1  per  cent.,  the  oils  tested 
ranging  in  viscosities  from  0.8  to  6.4  Poise  (approximately  385" 
to  2,900"  Redwood).  Individual  readings  of  the  ten  consecutive 
readings  on  the  Michell  instrument  differed  only  about  3  per 
cent,  at  the  maximum. 

Conversion  Tables. — The  Tables  Nos.  6,  7  and  8  have  been 
compiled  by  the  U.  S.  Bureau  of  Standards  (Report  of  Committee 
D-2,  American  Society  for  Testing  Materials). 

TABLE    6a. — MULTIPLYING   FACTORS  TO  CONVERT   ENGLER  NUMBERS  TO 
SAYBOLT  OR  TO  REDWOOD  TIMES 


Engler  number 

Factor  to  convert  Engler 
number  to  Saybolt  time 

Factor  to  convert  Engler 
number  to  Redwood  time 

1.00 

28.1 

26.7 

1.05 

28.4 

27.0 

.10 

28.8 

27.2 

.15 

29.1 

27.5 

.20 

29.5 

27.6 

.25 

29.8 

27.8 

.30 

30.2 

28.0 

1.36 

30.5 

28.2 

1.40 

30.8 

28.3 

1.45 

31.1 

28.5 

1.50 

31.4 

28.6 

1.60 

32.0 

28.8 

1.70 

32.5 

29.0 

1.80 

33.0 

29.2 

1.90 

33.5 

29.4 

2.00 

33.9 

29.6 

2.10 

34.2 

29.7 

2.20 

34.5 

29.9 

2.30 

34.8 

30.0 

2.40 

35.1 

30.1 

2.50 

35.3 

30.2 

2.60 

35.5 

30.3 

2.70 

35.7 

30.3 

^.80 

35.9 

30.4 

2.90 

36.1 

30.4 

3.00 

36.2 

30.5 

3.50 

36.7 

30.7 

4.00 

37.1 

30.9 

4.50 

37.3 

31.1 

5.00 

37.4 

31.2 

6.00 

37.5 

31.3 

8.00 

31.3 

50.00 


37.5 


31.3 


54  PRACTICE  OF  LUBRICATION 

TABLE  66.— MULTIPLYING  FACTORS  TO  CONVERT  SAYBOLT  TIMES  TO 
ENGLER  NUMBERS  OR  TO  REDWOOD  TIMES 


Saybolt  times,  seconds 

Factor  to  convert  Saybolt 
time  to  Engler  number 

Factor  to  convert  Saybolt 
time  to  Redwood  time 

28 

0.0357 

0.95 

30 

.0352 

.95 

32 

.0346 

.95 

34 

.0342 

.94 

36 

.0337 

.94 

38 

.0333 

.93 

40 

.0330 

.93 

42 

.0327 

.92    ' 

44 

.0323 

.92 

46 

.0320 

.92 

48 

.0317 

.91 

50 

.0314 

.91 

55 

.0308 

.90 

60 

.0302 

.89 

65 

.0297 

.88 

70 

.0293 

.87 

75 

.0289 

.86 

80 

.0286 

.86 

85 

.0284 

.86 

90 

.0282 

•.85 

95 

.0280 

.85 

100 

.0279 

.85 

110 

.0276 

.84 

120 

.0274 

.84 

130 

.0272 

.84 

140 

.0271 

.84 

160 

.0269 

.84 

180. 

.0268 

.84 

200 

.0267 

.84 

250 

.0267 

.84 

300 

.0267 

.84 

1800 

.0267 

.84 

Viscometers  should  be  calibrated  by  testing  the  viscosity  of  a 
standard  liquid,  as  water,  mixtures  of  glycerine  and  water,  cane 
sugar  solutions,  etc.  Rape  oil  or  sperm  oil  as  recommended  by 
some  for  standardizing  viscometers  vary  too  much  in  viscosity 
to  be  used  for  standardizing  purposes. 

It  is  important  that  the  efflux  tubes  should  not  wear  by  use,  as 
the  viscosity  readings  will  then  be  top  low.  Redwood  uses  an 
agate  tube  which  he  reports  has  shown  no  wear  over  a  number  of 
years.  Engler  uses  a  platinum  tube,  and  as  the  Engler  number  is 
given  as  compared  with  water,  the  instrument  is  frequently  cali- 
brated, and  slight  wear  of  the  tube  accordingly  does  not  affect 


TESTING  LUBRICANTS 


TABLE  6c. — MULTIPLYING  FACTORS  TO  CONVERT  REDWOOD  TIMES  TO 
SAYBOLT  TIMES  OR  TO  ENGLER  NUMBERS 


Redwood  time 

Factor  to  convert  Redwood 
times  to  Saybolt  time 

Factor  to  convert  Redwood 
to  Engler  number 

28      . 

.05 

0.0377 

29 

.05 

.0372 

30 

.08 

.0368 

32 

.06 

.0364 

34 

.07 

.0361 

36 

1.07 

.0358 

38 

1.08 

.0355 

40 

1.09 

.0353 

42 

1.09 

.0351 

44 

1.10 

.0349 

48 

1.11 

.0347 

48 

1.12 

.0345 

50 

1.13 

.0344 

55 

1.14 

.0340 

60 

1.15 

.0337 

65 

1.16 

.0335 

70 

1.16 

.0333 

75 

1.17 

.0331 

80 

1.18 

.0330 

85 

1.18 

.0339 

90 

.19 

.0388 

95 

.19 

.0327 

100 

.19 

.0386 

110 

.19 

.0325 

120 

.20 

.0384 

130 

.20 

.0328 

140 

.20 

.0381 

160 

1.20 

.0321 

180 

1.20 

.0320 

200 

1.20 

.0320 

250 

1.20 

.0320 

300 

1.20 

.0320 

1500 

1.20 

.0320 

the  accuracy  of  the  Engler  numbers.  The  Saybolt  instrument 
has  a  bronze  efflux  tube,  carefully  calibrated. 

When  particulars  of  the  viscosity  of  an  oil  are  given,  important 
details  are  often  omitted.  Sometimes  the  name  of  the  viscometer 
is  not  given,  or  the  temperature  at  which  the  viscosity  is  taken. 
Further,  if  it  is  desired  to  calculate  the  absolute  or  the  specific 
viscosity,  it  is  necessary  also  to  know  the  specific  gravity. 

Temperatures. — -Viscosity  figures  quoted  at  70°F.  are  going  out 
of  use,  and  rightly  so,  as  the  oil  is  very  rarely  at  this  temperature 
during  actual  use.  For  oils  used  externally,  the  important  vis- 


56 


PRACTICE  OF  LUBRICATION 


cosities  are  those  taken  at  104°F.  (40°C.)  and  140°F.  (60°C.) 
as  the  temperature  of  the  oil  film  will  range  somewhere  between 
30°C.  and  50°C.  for  ordinary  bearings  and  between  50°C.  and 
70°C.  for  bearings  in  steam  turbines,  enclosed  high  speed  steam 
engines  and  many  internal  combustion  engines. 

For  steam  cylinder  oils  the  viscosity  should  be  taken  at  212°F. 
To  test  the  viscosity  at  higher  temperatures  in  addition  to  the 
212°F.  figure  does  not  appear  to  be  of  any  value;  although  vis- 
cosity is  important,  there  are  other  and  more  important  proper- 
ties than  viscosity  which  determine  the  lubricating  quality  of 
cylinder  oils. 

For  oils  like  air  compressor  oils  and  internal  combustion  engine 
oils,  where  fairly  low  viscosity  oils  are  used,  the  viscosity  should 
be  measured  at  104°F.  and  212°F. 

When  the  setting  point  of  an  oil  is  known  and  at  least  two  vis- 
cosities, preferably  three,  a  viscosity  curve  can  easily  be  drawn 
from  which  can  be  measured  the  approximate  viscosity  figures 
at  intermediate  temperatures.  Commercial  measurements  of 
viscosity  are  usually  accurate  within  one  per  cent. 

Oils  change  in  viscosity  with  change  in  temperature  (ranging 
normally  from  .6  per  cent,  to  6.0  per  cent,  per  °F.  between  104°F. 
and  212°F.)  The  change  per  °F.  is  greater  for  mineral  oils  than 
for  fixed  oils,  greater  for  high  viscosity  oils  than  for  low  viscosity 
oils,  greater  (at  high  temperatures)  for  asphalt ic  base  and  Rus- 
sian oils  than  for  paraffin  base  oils.  The  increase  per  °F.  be- 
comes very  great  when  approaching  the  setting  point  temperature 
of  the  oil.  As  non-paraffinic  base  oils  have  low  setting  points, 
their  increase  in  viscosity  at  low  temperatures  is  usually  less 
than  for  paraffin  base  oils.  Hence,  for  cold  conditions  or  climates 
the  former  oils  have  better  viscosity  curves  at  the  working  tem- 
peratures. 

The  following  figures  show  the  difference  in  character  between 
paraffin  base  and  non-paraffinic  base  oils. 


Saybolt  viscosity 

Californian 
oil 

Russian 
oil 

Paraffin 
base  oil 

Texas 
oil 

Paraffin 
base  oil 

At  212°F  

48 

51 

49 

73 

74 

At  140°F  

147 

i  £n 

i  in 

ofif) 

OCA 

At  104°F  

430 

400 

9fiQ 

1  900 

7OO 

Cold  test  

0°F. 

0°F. 

25°F. 

20°F. 

40°F. 

Average  change  in  viscos- 

ity per  deg.  F.  in  % 

From  212°F.  to  140°F.  .  . 
From  140°F.  to  104  °F.  .  .  . 

2.9% 

5.4% 

2.7% 
4.6% 

1-7% 
4.0% 

5.4% 
6.5% 

3.3% 
5.0% 

TESTING  LUBRICANTS  57 

At  temperatures  below  104°F.  the  viscosity  curves  are  very 
steep  and  the  increase  in  viscosity  per  °F.  is  still  higher,  particu- 
larly so  for  oils  having  poor  cold  tests,  as  is  the  case  with  paraffin 
base  oils,  or  mixtures  containing  poor  cold  test  cylinder  stock  or  a 
large  amount  of  fixed  oil  or  fat.  When  the  viscosity  curve  is  very 
steep  around  70°F.  it  means  that  if  the  oil  is  supplied  through 
gravity  feed  oilers,  syphon  oilers  and  the  like,  even  slight  changes 
in  temperature  will  appreciably  affect  the  oil  feed  which  is  an 
undesirable  feature. 

At  high  temperature  the  fixed  oils  maintain  their  viscosities 
remarkably  well,  which  is  probably  one  of  the  reasons  why  fixed 
oils  are  better  lubricants  for  bearings  which  are  inclined  to  heat 
because  of  bad  mechanical  conditions,  excessive  bearing  pres- 
sures, etc. 

The  viscosity  of  oils,  when  measured  under  great  pressure1  is 
much  greater  than  the  ordinary  viscosities,  which  are  measured 
under  atmospheric  pressure;  the  increase  in  viscosity  is  several 
times  greater  for  mineral  oils  than  for  fixed  oils. 

When  oils  are  standardized  for  viscosity,  it  is  customary  to 
allow  a  manufacturer's  variation  of  4  per  cent,  to  6  per  cent,  above 
and  2  per  cent,  to  3  per  cent,  below  the  standard;  the  permissible 
variation  above  the  standard  is  the  greater  of  the  two,  because  too 
high  a  viscosity  is  usually  less  objectionable  under  the  conditions 
of  service  than  too  low  a  viscosity. 

Comparing  two  oils  having  the  same  kinematic  viscosity,  say 
the  same  Saybolt  viscosity,  the  heavier  oil  of  the  two  (the  one 
having  the  highest  specific  gravity)  really  is  the  more  viscous, 
because  being  heavier  it  flows  out  of  the  viscometer  more  rapidly 
than  it  would  if  it  were  lighter  in  specific  gravity.  The  real  vis- 
cosities of  non-paraffin  base  oils  are  therefore  about  5  per  cent, 
higher  than  their  kinematic  viscosities  lead  one  to  expect,  when 
comparing  them  with  paraffin  base  oils.  Much  confusion  has  been 
caused  by  expressing  the  viscosities  of  oils  in  terms  of  kinematic 
viscosities,  and  it  would  be  very  desirable  if  users  of  oil  would 
insist  upon  viscosities  being  measured  or  specified  as  absolute 
viscosities,  which  represent  their  true  viscosities  and  consequently 
form  a  much  better  basis  for  comparing  the  utility  or  suitability 
of  different  oils. 

The  viscosity  is  frequently  the  most  important  property  of  a 
lubricating  oil.  With  perfectly  lubricated  frictional  surface 
(complete  oil  film)  the  friction  is  directly  proportional  to  the  vis- 
cosity of  the  oil  and  mineral  oils  are  always  used.  With  less  per- 

1  Experiments  by  Dr.  T.  E.  Stanton  and  Mr.  I.  H.  Hyde,  Nat.  Phys. 
Lab.,  Teddington. 


58  PRACTICE  OF  LUBRICATION 

fcctly  lubricated  surfaces  the  oiliness  of  the  oil  becomes  important 
and  compounded  oils  are  frequently  used.  Under  very  severe 
conditions  of  pressure  (incomplete  oil  film)  the  viscosity  value 
of  the  lubricant  is  no  guide  at  all;  the  oiliness  becomes  the  all- 
governing  factor,  and  fixed  oils  or  oils  very  rich  in  fixed  oils  have 
to  be  used. 

Speaking  generally,  high  viscosity  oils  are  required  for  condi- 
tions of  high  temperature  or  great  pressure  or  slow  speed.  Low 
viscosity  oils  are  required  for  conditions  of  Jow  pressure  or  high 
speed.  For  low  temperature  conditions  it  is  low  setting  point 
that  governs  the  selection  of  oil  more  than  viscosity. 

Viscosity  of  Semi-solid  Lubricants. — Cup  greases,  solidified 
oils,  etc.,  are  generally  sold  in  five  standard  consistencies,  very 
soft,  soft,  medium,  hard  and  very  hard. 

The  consistency  varies  with  the  temperature  of  the  grease  and 
it  is  a  matter  of  personal  judgment  developed  by  experience 
what  the  consistency  of  a  sample  of  grease  is.  Several  attempts 
have  been  made  to  devise  an  instrument  for  measuring  the 
consistency — viscosity — of  a  grease,  but  none  have  been  of  any 
practical  value.  Several  instruments  have  a  weighted  needle, 
which  is  allowed  to  penetrate  for  a  certain  number  of  seconds, 
or  until  it  stops  due  to  skin  friction;  the  observations  are  very 
irregular  even  with  the  same  sample  of  grease,  due  to  local  varia- 
tions in  consistency.  In  other  instruments  the  grease  is  squeezed 
through  a  small  opening  by  a  definite  force;  here  again  results 
are  most  erratic  and  misleading. 

One  reason,  probably  the  chief  reason,  for  these  failures  is  that 
all  greases  have  a  peculiar  "set"  or  " honeycomb"  nature;  once 
the  grease  has  been  handled,  the  honeycomb  structure  is  broken 
up  and  the  grease  becomes  softer  and  more  oily  in  appearance. 
To  show  this  effect,  the  author  forced  a  certain  amount  of  a 
medium  cup  grease  through  a  %-inch  nozzle  by  the  force  of  a 
28-lb.  weight.  The  grease  came  through  the  first  time  in  126 
seconds.  On  putting  the  same  grease  back  in  the  test  cup  and 
repeating  the  performance,  the  efflux  times  for  the  succeeding 
three  tests  were:  47  seconds,  13  seconds,  and  6  seconds. 

Many  engineers  will  have  noticed  that  when  working  grease 
by  the  fingers  and  hand  it  becomes  softer  and  softer.  The  author 
also  tried  various  petroleum  jelly  greases  by  a  grease  viscometer 
and  found  the  results  fairly  consistent,  presumably  because  these 
greases  do  not  possess  that  peculiar  structure  characteristic 
of  cup  greases  and  other  soap-containing  greases. 

Capillarity.— All  lubricating  oils  have  the  property  of  rising 
into  syphons  or  wicks  made  of  wool  or  cotton,  but  their  capillary 
power  differs  considerably  for  different  oils. 


TESTING  LUBRICANTS  59 

Railway  and  steamship  companies,  many  of  which  employ  to  a 
large  extent  syphon  lubrication  or  pad  lubrication,  find  it  very 
useful  to  compare  lubricating  oils  for  capillary  power,  as  it  is 
upon  this  property  that  their  syphoning  ability  largely  depends. 
Obviously,  the  best  method  is  to  test  the  oils  in  an  actual  box  of 
the  exact  type  used  on  the  railway  or  steamer,  and  to  test  the 
oils  over  the  whole  range  of  temperatures  to  which  they  may  be 
exposed  during  service. 

The  quality  of  the  wool  is  important.  Berlin  wool,  which  is  of 
a  soft  loose  texture,  has  greater  syphoning  ability  than  closely 
twisted  worsted  yarn. 

The  syphoning  ability  of  lubricating  oil  is  largely  influenced 
by  the  viscosity  of  the  oil  and  by  its  nature,  whether  pure  mineral 
or  containing  a  percentage  of  fixed  oil.  The  lower  the  viscosity 
the  quicker  will  the  oil  syphon  from  the  lubricator  cup  into  the 
bearing. 

Emulsification. — Circulation  oils  which  are  used  in  connection 
with  steam  turbines,  enclosed  type  steam  engines,  etc.,  come  into 
contact  with  water  and  must  not  form  an  emulsion  with  water. 
Animal  and  vegetable  oils  emulsify  quickly  when  churned  to- 
gether with  water,  so  that  it  is  out  of  the  question  to  use  these 
oils  in  circulation  systems  where  there  is  danger  of  water  being 
present.  Mineral  lubricating  oils  have  a  low  affinity  for  water, 
but  experience  has  proved  that  it  is  sufficiently  strong  in  most  of 
them  to  cause  frequent  trouble.  The  tendency  to  emulsify 
differs  considerably  for  different  oils,  and  it  therefore  becomes 
necessary  to  subject  circulation  oils  to  an  emulsification  test. 

This  test  may  be  carried  out  by  shaking  definite  quantities 
of  oil  and  water  either  by  a  reciprocating  motion  in  a  bottle  or  by 
churning  the  oil  and  water  together  by  a  paddle  wheel  revolving 
at  high  speed.  The  water  may  be  either  distilled  water,  salt 
water,  or  a  caustic  soda  solution,  according  to  the  requirements 
which  the  oil  has  to  meet.  Marine  turbine  oil  for  example  must 
separate  from  salt  water  in  such  cases  where  a  leakage  of  salt 
water  into  the  system  cannot  easily  be  prevented. 

Where  boilers  prime  and  boiler  impurities  are  likely  to  be  car- 
ried over  into  steam  turbines  or  enclosed  type  steam  engines, 
it  may  be  of  interest  to  use  a  caustic  soda  solution  or  even  the 
boiler  water  itself  when  making  the  emulsification  test. 

The  test  should  be  carried  out  at  about  130°F.  which  is  the 
average  temperature  of  circulation  oils  when  in  service,  and  the 
mixture  should  be  allowed  to  settle  at  a  similar  temperature. 

Ferric  oxide  or  iron  salts  have  a  most  powerful  emulsifying 
effect  on  circulation  oils  in  the  presence  of  water.  If  only  a 


60  PRACTICE  OF  LUBRICATION 

fraction  of  1  per  cent,  iron  salts  is  added  to  the  water  used  for 
the  emulsification  test  nearly  all  oils  will  show  a  very  consider- 
able percentage  of  sludge.  It  will  appear  that  it  is  the  presence 
of  a  quite  small  percentage  of  certain  unstable  hydrocar- 
bons, sulphur  compounds,  naphthene  salts,  etc.,  which  causes 
emulsification. 

Neutral  filtered  oils  show  less  tendency  to  emulsification  than 
acid  treated  oils  and  should  therefore  be  used  in  preference  to  the 
latter  oils  in  the  manufacture  of  circulation  oils.  As  most 
neutral  filtered  oils  have  a  low  viscosity,  it  becomes  necessary 
to  mix  them  with  filtered  cylinder  stock  when  manufacturing 
heavy  viscosity  circulation  oils.  Filtered  cylinder  stock  has  not 
been  treated  with  acid,  but  merely  filtered  to  remove  unstable 
hydrocarbons,  etc.,  and  is  therefore  eminently  suitable  for  the 
purpose.  Well  filtered  cylinder  stocks  have  only  a  slight  ten- 
dency to  emulsification. 

Speaking  generally,  low  viscosity,  low  specific  gravity  oils  give 
better  service  as  circulation  oils  than  heavy  viscosity,  heavy 
specific  gravity  oils,  because  they  separate  quicker  from  water, 
dirt  and  other  impurities. 

Attempts  have  been  made  to  express  the  tendency  of  an  oil  to 
emulsify  in  terms  of  its  " emulsification  value,"  an  emulsifica- 
tion value  of  98  per  cent,  meaning  that  98  per  cent,  of  oil  sepa- 
rated out  in  the  emulsification  test,  2  per  cent,  being  retained 
in  the  sludge. 

Even* if  an  oil  shows  great  resistance  to  emulsification,  it  is 
desirable  to  know  how  rapidly  the  separation  takes  place. 
When  in  an  emulsification  test  the  mixture  of  oil  and  water  is 
allowed  to  separate,  some  oils  will  separate  out  in  a  few  minutes, 
whereas  others  m&y  take  half  an  hour  or  more,  and  yet  the 
final  separation  may  not  show  any  formation  of  sludge. 
Obviously,  quick  separation  is  exceedingly  important,  as  in 
most  circulation  oiling  systems,  the  oil  is  not  given  much  time 
to  free  itself  from  water. 

An  apparatus  to  determine  the  demulsibility  (i.e.  resistance 
to  emulsification)  of  an  oil  and  to  express  same  by  a  figure  has 
been  devised  by  W.  H.  Herschell  (described  in  U.  S.  Dept.  of 
Commerce,  Bulletin  No.  86).  It  consists  of  a  100  c.c.  glass 
container,  with  an  internal  diameter  of  approximately  26  mm. 
into  which  is  poured  20  c.c.  of  the  oil  to  be  tested  and  40  c.c. 
of  distilled  water  (or  other  water,  as  may  be  desired).  A  paddle 
89  mm.  long,  20  mm.  wide  and  1.5  mm.  thick  is  connected  to 
and  driven  by  a  vertical  electric  motor  at  a  speed  of  1,500  r.p.m. 
The  glass  container  is  placed  in  a  brass  vessel  filled  with  water 


TESTING  LUBRICANTS  61 

and  heated  by  a  Bunsen  burner  to  maintain  the  oil  and  water 
mixture  in  the  glass  container  at  a  temperature  of  55°C. 
(131°F.)  during  the  test.  The  oil  and  water  are  churned  by 
the  paddle  for  five  minutes,  the  container  then  lowered  free  of 
the  paddle  and  a  record  taken  of  the  time  in  minutes  taken  for 
separation. 

The  demulsibility  figure  (D)  is  calculated  as  the  rate  of  oil 
settling  out  per  hour,  and  is  therefore  expressed  as: 

D  =  60  X  7 

§ 

where:  v  is  the  volume  OT  oil  in  c.cs.  which  has  separated  out. 
t  is  the  time  in  minutes  taken  for  the  oil  to  separate  out. 

The  maximum  demulsibility  figure  is  1,200,  i.e.,  the  entire 
volume  of  oil  (20  ccs.)  separates  out  in  60  seconds.  If  with  a 
poor  oil  only  10  ccs.  separate  out  in  say  15  minutes,  the  demulsi- 
bility value  is: 

60  X  ijr  =  40 

Surface  Tension. — There  can  be  no  doubt  that  the  surface 
tension  of  an  oil  has  some  influence  on  the  condition  and  strength 
of  thin  oil  films  in  contact  with  metallic  surfaces.  Lubricating 
oils  wet  metallic  surfaces,  as  their  surface  tensions  are  lower  than 
those  of  metals.  Differences  in  surface  tension  as  between  vari- 
ous lubricants  will  therefore  mean  different  behavior  as  to  their 
tendency  to  wet  metallic  surfaces,  but  the  exact  nature  and 
importance  of  surface  tension  in  connection  with  lubrication  is 
still  a  practically  unexplored  subject. 

CHEMICAL  TESTS 

Acidity. — -Free  acid  in  lubricating  oils  may  be  present  as  free 
mineral  acid,  petroleum  acid,  fatty  acid  or  rosin  acid. 

(a)  Free  sulphuric  acid  or  other  mineral  acid  which  has  been 
used  in  the  refining  of  the,  oil.  It  is  very  rare  nowadays  to  find 
any  objectionable  percentage  of  free  acid  from  this  source,  but 
in  the  case  of  transformer  and  switch  oils,  it  is  of  great  impor- 
tance that  the  percentage  of  mineral  acid  be  exceptionally  low,  so 
that,  whereas  for  ordinary  purposes  a  percentage  of  0.03  in  terms 
of  S.O3  may  be  permitted,  the  percentage  in  the  case  of  trans- 
former oils  must  not  exceed  0.01, 

(6)  Petroleum  acid  may  be  present  in  the  original  crude  or 
may  be  produced  during  distillation  and  refining.  Petroleum 
acids  develop  in  circulation  oils  during  continuous  use,  due  to 


62  PRACTICE  OF  LUBRICATION 

oxidation.  Petroleum  acids  are  very  weak  in  their  action  and  do 
not  affect  metals  except  lead  and  zinc;  mineral  oils  usually  con- 
tain less  than  0.01  per  cent,  of  petroleum  acids,  but  the  presence  of 
a  larger  percentage  is  not  harmful  as  long  as  the  percentage  does 
not  exceed  0.3  per  cent,  in  terms  of  SO3  (used  circulation  oils). 

(c)  Free  fatty  acid  is  only  present  in  lubricating  oils  which  con- 
tain fixed  oils.     The  percentage  of  free  fatty  acid  in  a  fixed  oil 
is  not  objectionable  as  long  as  it  does  not  exceed  0.5  per  cent,  in 
terms  of  S03.     A  higher   percentage   of  acid  is  permissible  in 
certain  cutting  oils.     A  mixture  of  fixed  oil  and  mineral  oil  will 
of  course  contain  proportionally  less  of  free  fatty  acid  the  greater 
the  percentage  of  mineral  oil. 

When  the  contents  of  free  fatty  acid  is  high  in  a  lubricating  oil 
it  has  the  effect  of  attacking  the  metallic  surfaces  with  which  the 
oil  comes  into  contact.  Metallic  soaps  are  formed,  which  choke 
up  the  oil  pipes  and  lubricating  channels  in  the  machinery.  In 
contact  with  brass  parts  verdigris  is  formed.  The  softer  metals 
like  lead  and  zinc  are  very  quickly  attacked  and  the  effect  is 
marked  in  bearings  lined  with  white  metal  containing  a  high 
percentage  of  these  metals.  • 

When  oils  containing  fatty  oils  are  stored  in  storage  tanks  or 
cabinets  which  are  either  unlined  or  merely  galvanized  the  free 
fatty  acid  attacks  the  metal  surface,  forming  metallic  soaps.  It 
has  been  found,  however,  that  tin  is  not  attacked  to  any  degree 
by  the  free  fatty  acid  and  for  this  reason  all  oil  cabinets  and  oil 
tanks  should  be  tinned  on  surfaces  in  contact  with  the  oil. 
This  also  applies  to  other  parts  of  the  cabinets,  such  as  oil  pumps, 
strainers,  etc. 

During  continuous  use  all  oils  containing  fixed  oils  oxidize  (air) 
and  hydrolize  (moisture) ,  the  result  of  which  is  the  formation  of  free 
fatty  acid  and  of  sticky  gummy  varnish-like  deposits,  which  may 
cause  trouble. 

(d)  Rosin  acids  indicate  the  presence  of  rosin  or  rosin  oil  which 
is  always  objectionable  in  lubricating  oils. 

Saponification  Value.— The  saponifkation  value  is  the  number 
of  grams  of  potash  (KOH)  required  to  saponify  the  fatty  (vege- 
table or  animal)  constituents  present  in  1,000  grams  of  the  oil. 
The  saponification  value  is  therefore  useful  in  determining  the 
character  and  percentage  of  a  fixed  oil  present  in  a  mixture  of 
fixed  oil  and  mineral  oil.  When  there  are  two  or  more  grades 
of  fixed  oil  present  it  is  difficult  to  identify  them  with  certainty. 

Iodine  Value.— The  iodine  value  is  the  number  of  grams  of 
iodine  absorbed  by  the  unsaturated  constituents  present  in  100 
grams  of  the  oil. 


TESTING  LUBRICANTS  63 

It  has  been  mentioned  that  fixed  oils  have  a  great  affinity  for 
oxygen  and  that  during  continual  use  they  will  oxidize  and  form 
deposits.  The  iodine  value  is  an  indication  of  this  tendency  and 
is  based  on  the  fact  that  iodine  will  quickly  combine  with  those 
ingredients  in  the  oil  which  have  a  tendency  to  oxidize. 

As  might  be  expected  the  iodine  value  of  drying  oils  like  lin- 
seed oil  is  very  high,  whereas  the  iodine  value  of  mineral  lubricat- 
ing oil  is  very  low.  Below  is  given  typical  iodine  values  for 
various  oils : 

Drying  oils,  such  as  linseed  oils Above  170 

Semi-drying  oils,  such  as  cottonseed,  ravison  rape, 

fish  and  whale  oils From  100  to  170 

Non-drying  oils,  such  as  animal  oils,  (except  whale 
oil),  and  vegetable  oils  (except  cottonseed  and 

ravison  rape) 50  to  100 

Scotch  shale  oil  0.890 23 

Russian  mineral  lubricating  oils 7 

American  mineral  lubricating  oils  (paraffin  base) .  .    10  to  16 

The  cause  of  the  high  iodine  value  of  Scotch  shale  oil  is  the 
large  percentage  of  unsaturated  hydrocarbons  present  in  this  oil. 

Oxidation  and  Gumming. — In  order  to  get  an  idea  of  the  tend- 
ency of  lubricating  oils  to  oxidize  and  gum,  many  tests  have  been 
devised;  in  one  test  one  gramme  of  the  oil  is  heated  on  a  watch 
glass  for  a  certain  length  of  time  at  certain  temperatures, 'after 
which  the  oil  is  examined.  Another  test  measures  the  increase 
in  weight,  i.e.,  the  amount  of  oxygen  absorbed  and  the  percentage 
of  free  fatty  acid  formed.  All  such  tests  are  of  value  in  compar- 
ing one  oil  with  another.  The  iodine  value,  however  appears 
to  be  the  nearest  approach  to  a  correct  indication  of  the  tendency 
of  an  oil  to  oxidize. 

Under  " Color"  it  was  mentioned  that  the  color  of  an  oil  is 
clue  to  the  presence  of  unsaturated  hydrocarbons.  It  is  there- 
fore to  be  expected  that  oils  dark  in  color  are  more  easily 
oxidized  than  pale  oils,  and  experience  has  proved  this  to  be  the 
case.  Where  machinery  is  exposed  to  sunlight,  as  for  instance, 
steam  rollers,  steam  tractors,  etc.,  it  has  been  found  that  red  oils 
produce  a  tenacious  dark  brown  skin  on  the  metal  parts,  whereas 
pale  asphaltic  base  oils  have  very  much  less  tendency  to  form  such 
deposits. 

Frequent  complaints  have  also  been  made  that  machine, parts 
in  engine  rooms  get  tarnished,  also  the  bright  parts  of  spindle 
frames  in  textile  mills  unless  very  pale  oils  are  used.  This  tar- 
nishing effect  is  very  unsightly  in  the  case  of  high-class  machine 
tools,  In  order  to  avoid  machine  parts  becoming  tarnished,  it  is 


64  PRACTICE  OF  LUBRICATION 

therefore  best  to  use  pale  colored  oils,  either  straight  mineral  or 
mixed  with  a  small  percentage  of  animal  oil.  The  presence  of  the 
animal  oil  has  a  peculiar  effect,  making  it  quite  easy  to  wipe  the 
bright  parts  clean.  Possibily,  the  free  fatty  acid  present  is 
helpful,  preventing  the  film  from  forming,  owing  to  a  .very 
slight  corrosive  action  between  the  acid  and  the  metal.  An 
admixture  of  vegetable  oil  would  increase  the  oxidizing  tendency 
of  the  oil. 

For  oils  which  are  used  in  connection  with  transformers  and 
air  compressors,  it  is  obvious  that  they  must  have  the  smallest 
possible  tendency  to  combine  with  the  air.  Circulation  oils  (for 
steam  turbines,  etc.)  are  also  in  more  or  less  contact  with  air  and 
therefore  subject  to  oxidation.  It  would  therefore  seem  desirable 
to  examine  oils  to  be  used  for  such  purposes  by  subjecting  them 
to  an  oxidation  test  on  lines  similar  to  the  sludging  test  described 
under  transformer  oils. 

Ash. — Ash  is  present  in  appreciable  quantities  only  in  lubri- 
cating oils  which  have  been  soap  thickened  or  badly  refined. 
Distilled  mineral  lubricating  oils  should  not  contain  more  than 
0.02  per  cent,  ash,  and  for  undistilled  oils  like  steam  cylinder  oils, 
the  ash  should  be  less  than  0.1  per  cent.  The  ash  may  consist  of 
iron  rust  from  the  still  or  it  may  be  alkali  from  the  refining. 

Carbon  Residue. — Oils  which  during  use  are  vaporized  or 
burnt,  as  is  the  case  with  all  oils  used  for  internal  combustion 
engines,  produce  more  or  less  carbon  deposit.  It  is  difficult  to 
duplicate  these  conditions  in  a  laboratory  test,  but  it  would  seem 
desirable  to  have  some  kind  of  a  test  for  the  tendency  to  carbonize, 
the  results  to  be  compared  with  actual  practice  in  order  to 
ascertain  its  value. 

One  apparatus  has  been  suggested  by  P.  H.  Conradson,  as 
illustrated.  This  method  is  a  modification  of  his  original  method 
and  apparatus  for  carbon  test  and  ash  residue  in  petroleum  lubri- 
cating oils.  (See '"  Proceedings  Eighth  International  Congress 
of  Applied  Chemistry,"  New  York,  September  1912,  Vol.  1, 
page  131.  Also  reprint  in  the  "Journal  of  Industrial  and 
Engineering  Chemistry,"  Vol.  4,  No.  11,  November,  1912.) 

Description  of  Conradson's  Apparatus  (Fig.  3).— (a)  Porcelain  cruci- 
ble; wide  form,  glazed  throughout,  25  to  26  c.c.  capacity,  46  mm.  in 
diameter. 

(b)  Skidmore  iron  crucible  45   c.c.  (iy2  oz.),  65  mm.  in  diameter, 
37  to  39  mm.  high,  with  cover,  without  delivery  tubes  and  one  opening 
closed. 

(c)  Wrought  iron  crucible  with  cover,  about  180  c.c.  capacity,  80 
mm.  diameter,  58  to  60  mm.  high.     About  10  mm.  of  sand  placed  in 
bottom  to  bring  Skidmore  crucible  nearly  flush  with  top. 


TESTING  LUBRICANTS 


65 


(d]  Triangle  medium  size,  pipe  stem  covered,  projection  on  side  to 
allow  flame  to  reach  all  sides  of  the  crucible. 

(e)  Sheet  iron  or  asbestos  hood  5  inches  in  diameter  and  2  inches 
high  provided  with  slanting  roof  %  of  an  inch  high,  terminating  into 
chimney,  the  chimney  being  2  inches  high,  and  2%  to  2%  inches  in 
diameter.     This  serves  to  distribute  the  heat  uniformly. 

(/)  Asbestos  or  sheet  iron,  block,  6  to  7  inches  square,  and  \y±  inches 
to  \y%  inches  high,  provided  with  opening  in  centre  which  is  3}£ 
inches  in  diameter  at  the  bottom,  and  3^  inches  in  diameter  at  the 


Z^^  , 

FIG.  3. — Conradson's  carbon  residue  apparatus. 


top  of  the  block.  This  block  acts  as  a  shield  for  the  flame  resulting 
in  even  distribution  of  the  flame  around  the  iron  crucible  during  the 
test. 

(g)  Tripod :  Tripod  or  stand  should  be  of  such  height  that  the  distance 
between  top  of  burner  and  bottom  of  large  iron  crucible  is  1  to  1>£ 
inches  depending  upon  the  kind  of  burner  used. 

(h)  Gas  Burner:  Where  gasoline  or  artificial  gas  is  used  the  Me*ker 
or  Scimatco  burner  155  mm.  in  height  having  24  mm.  section  of  flame  is 
recommended.  With  natural  gas  the  above  burners  or  any  improved 
form  of  Bunsen  burner  may  be  used. 

5 


66  PRACTICE  OF  LUBRICATION 

Method  of  Test. — Weigh  10  grams  of  the  oil  to  be  tested  into  a  tarred 
porcelain  crucible  and  place  the  latter  in  the  centre  of  the  Skidmore 
crucible.  Place  the  Skidmore  crucible  in  the  exact  centre  of  the  iron 
crucible,  and  put  on  the  covers  of  the  Skidmore  crucible  and  iron  crucible. 
Set  the  apparatus  up  as  indicated  in  Fig.  1. 

Heat  is  applied  to  the  apparatus  with  a  Bunsen  or  other  burner  with 
a  hot  flame  for  from  four  to  seven  minutes  depending  upon  the  body  of 
the  oil  being  tested;  this  flame  should  encompass  as  far  as  possible  the 
whole  crucible;  it  must  then  be  reduced  to  two  or  three  inches  and  the 
first  appearance  of  vapors  carefully  watched  for  after  the  period  of 
strong  heating  is  over,  in  order  that  the  vapor  flame  may  not  get  too  high 
and  the  oil  in  the  crucible  not  be  in  danger  of  boiling  over.  The  flame 
should  never  get  more  than  three  inches  above  the  chimney  and  it 
should  be  kept  at  an  average  of  about  two  inches  above  it  during  the 
period  in  which  vapors  come  off.  After  the  vapors  cease  to  be  evolved 
(as  evidenced  by  the  inability  to  ignite  them)  the  heat  is  increased  to  a 
maximum  obtainable  and  maintained  for  five  minutes.  The  bottom 
of  the  iron  crucible  should  be  red  hot;  then  allow  to  cool  for  five  minutes 
with  the  chimney  removed,  transfer  the  crucible  to  a  desiccator,  cool  and 
weigh.  The  entire  procedure  should  be  completed  in  about  thirty 
minutes  depending  upon  the  nature  of  the  oil. 

Precautions. — (1)  The  first  appearance  of  vapors  must  be  watched 
for  very  closely;  the  burner  may  be  momentarily  removed  occasionally 
to  facilitate  seeing  them.  From  experience  the  range  of  four  to  seven 
minutes  with  a  Bunsen  or  Tirril  burner  appears  to  be  about  right  for 
oils  varying  between  a  gun  oil  and  a  Liberty  Aero  Oil,  but  this  time 
will  vary  with  the  gas  and  burner  obtainable.  It  is  therefore  necessary 
that  very  close  attention  be  paid  to  the  operation  at  this  point. 

2.  If  the  vapors  get  too  high  at  any  time  the  burner  may  be  removed 
for  short  periods  although  this  is  not  advisable  if  it  can  be  reduced  suf- 
ficiently low  to  keep  the  vapors  ignited  about  two  inches  above  the 
chimney. 

3.  Dimensions  of  the  apparatus  as  shown  must  be  strictly  adhered  to. 

Asphalt  and  Tar. — It  is  seldom  necessary  to  test  lubricating 
oils  for  the  presence  of  asphalt  and  tar,  except  in  the  case  of  dark 
cylinder  oils,  particularly  those  used  for  superheated  steam. 

A  distinction  is  made  between  hard  asphalt  and  soft  asphalt, 
the  hard  asphalt  being  the  more  objectionable  of  the  two,  as  it 
will  form  hard  brittle  carbonization  deposits  inside  the  engines. 

Filtered  cylinder  oils  contain  less  asphalt  than  dark  cylinder 
oils,  and  are  therefore  to  be  preferred  in  all  such  cases  where 
carbonization  ordinarily  may  be  expected  to  take  place. 

Oiliness.— The  property  in  a  lubricant  which  causes  it  to 
adhere  to  metallic  surfaces  is  generally  referred  to  as  its  oiliness. 
Experience  appears  to  have  shown  that  oiliness  bears  no  relation 
to  the  physical  properties  of  an  oil;  although  it  is  greater  for 


TESTING  LUBRICANTS  67 

heavy  viscosity  oils  than  for  low  viscosity  oils  of  the  same  char- 
acter, yet  two  oils  may  have  the  same  viscosity  and  the  oiliness 
be  much  greater  in  the  one  than  the  other.  It  is  common  knowl- 
edge that  all  fixed  oils,  or  mixtures  of  mineral  oils  and  fixed  oils, 
possess  greater  oiliness  than  straight  mineral  oils.  From  the 
writer's  experience  it  seems  also  certain  that  a  mixture  of  low 
viscosity  distilled  mineral  lubricating  oil  and  filtered  cylinder 
stock  has  greater  oiliness  than  a  distilled  mineral  lubricating 
oil  of  the  same  viscosity  as  the  mixture. 

No  means  have  as  yet  been  devised  by  which  the  power  of  a 
lubricant  to  adhere  to  metallic  surfaces  can  be  directly  measured; 
if  lubricated  surfaces  are  pulled  apart,  the  lubricating  film  itself 
is  severed,  but  the  lubricant  still  adheres  to  both  surfaces,  so  that 
it  is  only  the  cohesion  of  the  film  that  can  be  determined  in  this 
manner. 

That  distilled  lubricating  oils  are  improved  in  oiliness  by  the 
admixture  of  fixed  oil  or  filtered  cylinder  stock  may  perhaps  be 
explained  by  the  fact  that  molecules  of  the  fatty  oil  or  cylinder 
stock  adhere  to  the  metallic  surfaces  in  preference  to  the  mole- 
cules of  the  distilled  mineral  oils;  such  coating  of  the  surfaces 
with  strongly  adhering  molecules  would  explain  why  it  is  possible 
with  such  blended  oils  to  sustain  almost  as  great  pressures  as 
if  the  fixed  oil  or  filtered  cylinder  stock  were  used  alone. 

Impurities. — The  impurities  most  frequently  met  with  in 
lubricating  oils  are  dirt,  glue  and  water. 

Dirt. — Dirt  is  easily  detected  when  the  oil  is  transparent. 
It  is  more  difficult  in  the  case  of  dark  oils,  such  as  cylinder  oils 
and  the  like.  The  best  way  of  testing  a  lubricating  oil  for  dirt 
is  to  draw  a  few  gallons  of  oil  from  the  bottom  of  the  barrel 
or  the  tank  in  which  the  oil  is  stored,  and  then  strain  the  oil 
through  muslin  or  silk  cloth.  Anything  that  remains  on  the 
cloth  can  be  freed  from  oil  by  treatment  with  petrol,  and  it  is 
then  generally  easy  enough  by  the  aid  of  a  magnifying  glass  or 
perhaps  even  with  the  naked  eye  to  judge  what  the  impurities 
are. 

If  metallic  iron  in  the  form  of  iron  scale  is  present  (from  the 
steel  drum  or  barrel)  a  magnet  will  detect  it,  the  small  particles 
being  drawn  up  at  the  approach  of  the  magnet;  or  the  metallic 
ingredients  can  be  identified  chemically. 

Cotton  waste,  small  pieces  of  wood,  etc.,  are  easily  recogniz- 
able, and  it  is  not  unusual  that  they  find  their  way  into  the  oil 
when  the  barrel  is  being  broached. 

The  bung  should  be  loosened  by  striking  the  staves  with  a 
mallet  and  it  should  never  be  removed  by  the  use  of  an  augur. 


68  PRACTICE  OF  LUBRICATION 


.  —  Glue  is  used  in  forming  a  coating  on  the  inside  of 
wooden  barrels  and  serves  two  purposes:  firstly,  the  prevention 
of  oil  leakage  through  the  wooden  staves;  secondly,  the  prevention 
of  moisture  from  entering  the  oil. 

The  importance  of  the  first  mentioned  object  is  obvious  and  the 
desirability  of  preventing  moisture  from  entering  the  oil  is 
explained  in  the  next  paragraph  under  "water." 

Sometimes  large  quantities  of  glue  are  found  in  a  barrel  due 
to  the  barrel  not  having  been  properly  drained  of  the  hot  liquid 
glue  during  the  glueing  process.  The  glue  will,  however,  not 
mix  with  the  oil  except  in  the  presence  of  moisture,  and  can 
always  be  detected  easily  by  the  consumer,  when  the  oil  is  being 
strained  before  use.  If  the  glue  is  not  detected,  the  results  may 
be  disastrous,  as  it  will  cause  excessive  heating  and  wear  and 
develop  sticky  deposits  in  lubricators;  in  circulation  oiling  systems 
and  oil  pipes;  it  will  cause  irregular  working  of  lubricators, 
especially  those  having  fine  openings,  as  hydrostatic  displacement 
cylinder  lubricators.  When  such  fine  openings  get  choked, 
steam  valves  and  pistons  cry  out  for  oil  if  the  trouble  is  not 
observed  in  time. 

Water.  —  Water  gives  an  oil  a  cloudy  appearance  and  its 
presence  is  therefore  easily  perceived  in  oils,  which  in  dry  con- 
dition are  transparent. 

When  the  oil  is  heated  to  a  few  degrees  above  212°F.  it  will 
soon  become  transparent,  if  the  cloudiness  is  due  to  water;  and 
if  more  than  a  trace  of  moisture  is  present,  it  will  partly  evaporate 
and  partly  separate  out  as  visible  drops  of  water  at  the  bottom. 

Mineral  oils  are  more  easily  clarified  than  oils  containing 
fixed  oils,  as  the  latter  have  a  strong  affinity  for  water  and  easily 
become  emulsified. 

The  presence  of  even  a  trace  of  moisture  is  very  detrimental 
in  transformer  and  switch  oils.  A  simple  test  (apart  from  testing 
dielectric  strength  or  specific  resistance)  is  the  hot-iron  test. 
An  eight-ounce  bottle  is  half  filled  with  transformer  oil;  an 
iron  rod,  say  y±  of  an  inch  in  diameter  is  heated  for  about  Y^ 
an  inch  to  a  dull  red  heat  and  slowly  lowered  into  the  oil.  If 
more  than  0.01  per  cent,  of  water  is  present  the  tiny  particles 
of  water  will  suddenly  turn  into  steam  with  a  crackling  noise; 
if  no  water  is  present,  there,  will  only  be  a  slight  hissing  noise 
from  the  oil  vapors. 

The  presence  of  a  slight  amount  of  moisture  in  oils,  other  than 
transformer  and  switch  oils,  is  not  detrimental,  so  far  as  the 
influence  of  the  water  itself  is  concerned;  and  yet,  in  nearly  every 
case  where  the  oil  is  moist,  more  or  less  trouble  is  experienced. 


TESTING  LUBRICANTS  69 

Ring  spindles  and  other  textile  spindles  rust  and  run  warm; 
internal  combustion  engines  develop  an  excessive  amount  of  car- 
bon deposit;  the  pistons  heat  up  and  wear  rapidly;  the  oil  is 
reported  to  be  " thinner  than  usual"  (because  the  excessive 
heating  of  the  oil  film  thins  the  oil)  and  the  oil  comes  out  of 
the  pistons  and  bearings  in  a  chocolate  colored  or  blackened, 
dirty  condition. 

This  very  remarkable  effect  of  the  presence  of  small  amounts 
of  moisture  is  explained  by  the  fact  that  moisture  nearly  always 
gets  into  the  oil  through  exposure  of  the  wooden  barrels  to  the 
weather.  During  warm  and  rainy  weather  the  staves  expand 
and  absorb  moisture;  during  nights  they  contract  and  the  effect 
of  such  alternate  expansion  and  contraction  is  that  moisture 
gets  through  to  the  inside  of  the  staves,  loosens  and  dissolves 
some  of  the  glue  coating  and  spreads  it  throughout  the  contents 
of  the  barrel.  This  is  the  most  dangerous  form  in  which  glue 
can  be  present  in  the  oil  and  it  is  usually  the  glue  that  causes 
lubrication  troubles,  more  so  than  the  water.  Wooden  barrels, 
when  in  transit,  should  therefore  preferably  be  covered  with 
tarpaulins  and  should  be  stored  under  cover  in  a  dry  place. 
When  barrels  are  stored  out  of  doors  from  lack  of  space  under 
roof,  they  should  be  covered  with  waterproof  covering  or  stored 
on  their  sides;  when  stored  on  end  the  moisture  collects  over  the 
staves  and  there  is  a  greater  likelihood  of  the  water  getting 
inside  than  when  they  are  stored  on  their  sides. 

MECHANICAL  MEANS  OF  TESTING  LUBRICANTS 

Mechanical  Testing  Machines. — As  the  usual  physical  and 
chemical  tests  of  lubricants  do  not  always  definitely  indicate 
whether  one  oil  will  be  more  satisfactory  than  another  for  certain 
machines,  many  investigators  have  designed  friction  testing 
machines  with  a  view  to  comparing  the  lubricating  properties 
of  different  oils.  There  are  a  great  variety  of  these  machines, 
chiefly  for  testing  bearing  oils,  and  they  have  been  extremely 
useful  in  discovering  important  laws  of  friction  and  in  comparing 
the  efficiency  of  different  lubricating  systems.  The  results  of 
such  experimental  work  have  been  of  interest  to  oil  manufacturers 
and  lubrication  engineers,  but  from  an  oil  consumer's  point 
of  view  they  are,  speaking  generally,  of  no  value  so  far  as  the 
selection  of  suitable  oils  is  concerned. 

The  difficulty  is  that  the  testing  machine  has  only  one  bearing, 
usually  with  beautifully  finished  rubbing  surfaces  and  operated 
under  conditions  of  oil  feed,  pressure,  speed  and  temperature 


70  PRACTICE  OF  LUBRICATION 

quite  different  from  practical  conditions.  In  most  works  there 
are  such  a  variety  of  bearings  that  it  is  quite  impossible  to  repro- 
duce all  these  conditions  on  the  one  bearing  of  a  testing  machine. 

The  following  two  examples  may  prove  instructive: 

Example  1. — A  certain  Government  had  a  Lahmeyer  oil 
testing  machine,  with  which  all  of  the  oils  offered  by  yarious  firms 
were  tested.  The  oils  were  intended  to  be  used  on  the  propelling 
machinery  of  warships. 

In  the  Lahmeyer  testing  machine  two  heavy  flywheels  are 
carried,  one  on  each  end  of  a  shaft;  the  shaft  is  supported  by  a 
central  ring  oiling  bearing,  which  serves  for  testing  the  oil. 
The  machine  is  driven  by  an  electric  motor,  which  can  be  con- 
nected to  the  flywheel  shaft  by  a  pin  coupling.  The  method  of 
testing  is  as  follows: 

The  bearing  is  supplied  with  the  oil  to  be  tested.  The  motor  is 
started  and  the  flywheel  rotated  at  full  speed:  1,500  to  1,700 
r.p.m.  The  motor  is  then  uncoupled  and  the  time  noted  which 
elapses  before  the  flywheel  comes  to  rest. 

The  longer  the  time  taken  by  the  shaft  to  come  to  rest,  the  better 
is  the  quality  of  the  oil  supposed  to  be,  and  this  is  true  for  this 
particular  bearing. 

Before  the  next  sample  of  oil  is  tested  the  bearing  is  quickly 
cleaned  by  benzine  passed  through  it,  and  it  is  dried  out  with  an 
air  current. 

It  will  be  understood  that  an  oil  manufactured  to  meet  the 
conditions  of  a  high  speed  ring  lubricated  bearing  will  give  the 
best  results  when  tested  on  this  machine. 

In  order  to  convince  the  Government  in  question  as  to  the 
futility  of  testing  oils  in  this  manner,  a  good  dynamo  oil  was 
submitted  and  it  was  found  that  the  shaft  revolved  three  times 
as  long  as  with  the  marine  oil,  which  in  actual  practice  gave 
the  best  results.  It  was  obvious  to  every  one  concerned  that 
the  dynamo  oil  was  absolutely  unsuitable  for  the  work  required. 

Example  2. — One  of  the  best  oil-testing  machines  on  the  market 
is  Thurston's  machine.  The  machine  consists  of  a  fchaft  sup- 
ported by  two  bearings;  the  shaft  at  one  end  has  an  overhanging 
bearing  fitted  with  two  brasses,  on  which  the  oil  is  tested. 
Suspended  from  the  bearing  is  a  hollow  pendulum  containing  a 
spring,  by  means  of  which  a  certain  bearing  pressure  may  be 
maintained.  When  the  shaft  revolves  the  oil  film  interposed 
between  the  shaft  and  the  brasses  causes  the  pendulum  to  swing 
outward  and  it  remains  in  a  certain  position  according  to  the 
oil  in  use. 

The  less  the  out-swing,  the  less  is 'the  coefficient  of  friction 


TESTING  LUBRICANTS  71 

and  the  better  the  oil,  for  this  particular  bearing  and  for  the 
particular  conditions  prevailing. 

When  tests  were  carried  out  to  find  out  which  was  the  most 
suitable  oil  for  shafting  bearings  running  at  a  certain  speed  and 
bearing  pressure,  a  Thurston  testing  machine  was  made  to  run 
under  as  neajly  as  possible  similar  conditions;  it  was  found, 
however,  when  testing  different  oils  that  the  coefficient  of  friction 
was  the  least  for  pure  kerosene  which  would,  of  course,  be 
useless  for  the  lubrication  of  shafting  bearings. 

This  result  will  be  easily  understood  when  one  takes  into  con- 
sideration that  shafting  in  actual  practice  is  always  more  or  less 
out  of  line  and  that  the  bearing  surfaces  are  never  perfectly 
smooth.  The  pressure,  therefore,  will  not  distribute  itself  so 
uniformly  over  the  entire  bearing  surfaces,  as  will  be  the  case 
with  the  bearing  of  Thurston's  oil  tester. 

The  limitations  of  testing  machines  are  now  beginning  to  be 
generally  recognized;  it  is  only  where,  as  in  the  case  of  railways, 
a  great  many  bearings  are  alike  and  operating  under  similar 
conditions  that  it  seems  at  all  worth  while  to  attempt  the  con- 
struction of  a  testing  machine;  even  then  there  is  ample  evidence 
that  variations  in  the  results  obtained  with  the  same  oil  in  use, 
may  easily  amount  to  50  per  cent,  and  rarely  fall  below  10  per 
cent. 

The  author  feels  that,  from  the  consumer's  point  of  view,  the 
coefficient  of  friction  of  various  oils  as  determined  by  a  testing 
machine  is  not  of  much  use;  the  oil  which  gives  the  least  friction 
on  the  testing  machine  may  often  prove  to  be  unsuitable  in 
actual  use. 

In  the  foregoing  no  reference  has  been  made  to  testing  machines 
for  testing  oils  for  internal  lubrication  of  s,teamr  cylinders,  gas 
engines,  etc.  Not  a  few  attempts  have  been  made  in  these 
directions,  but  as  far  as  the  author  knows,  the  results  have  been 
of  doubtful  value,  if  not  altogether  misleading.  It  must  be 
kept  in  mind  that  in  the  internal  lubrication  of,  for  example, 
steam  cylinders  and  internal  combustion  engine  cylinders,  the 
lubrication  is  nearly  always  imperfect  and  subject  to  so  many 
influencing  factors  that  it  is  much  more  difficult  to  reproduce 
the  conditions  in  a  testing  machine  than  in  the  case  of  bearings. 
Besides,  the  value  of  a  lubricant  often  becomes  apparent  only 
after  several  weeks  or  months  of  use;  such  properties  as  tendency 
to  carbonize,  emulsify,  oxidize,  etc.,  may  become  of  paramount 
importance,  as  compared  with  the  friction-reducing  properties 
of  the  oil,  as  will  be  made  clear  later  on  in  the  various  chapters 
devoted  to  the  different  kinds  of  engines. 


72 


PRACTICE  OF  LUBRICATION 


Works  Tests. — :The  author  has  come  to  the  conclusion,  and 
most  lubrication  engineers  will,  he  feels  certain,  agree  with  him 
that  the  only  reliable  way  of  testing  lubricants  is  to  test  them  under 


FIG.  4. — Taking  the  temperature  of  a  ring  oiling  bearing. 

actual  working  conditions,  by  applying  them  to  the  machinery 
upon  which  they  are  to  be  used,  and  watching  the  results. 

Temperature  Tests. — The  simplest  method  of  comparing  two 
oils  is  to  compare  the  frictional  temperature  rise  of  typical 


FIG.  5. — Taking  the  temperature  of  a  pedestal  bearing. 

bearings,  using  first  one  oil  and  then  the  other.  Any  difference 
in  quality  or  suitability  between  the  two  oils  will  be  shown  by 
a  different  frictional  rise  in  temperature  above  the  surrounding 


TESTING  LUBRICANTS 


73 


air  temperature.  The  difference  in  temperature  between  a  bear- 
ing and  the  air  close  to  it  will  remain  the  same,  independent  of 
the  air  temperature,  as  long  as  the  same  oil  is  in  use. 

Figs.  4  and  5  show  the  method  of  taking  the  oil  temperature  of  a 
ring  oiling  bearing  and  a  pedestal  bearing.  In  the  first  case  the 
thermometer  bulb  is  immersed  in  the  oil;  in  the  second  case  the 
bulb  is  covered  with  a  lump  of  fairly  stiff  grease  or  putty,  so  that 
the  bulb  may  be  held  in  contact  with  the  metal  and  as  accurately 
as  possible  record  the  correct  temperature. 

The  following  is  a  typical  example  of  a  temperature  test  on  a 
ring  oiling  bearing,  comparing  a  viscous  oil  with  an  oil  of  the 
correct  light  body: 


Time 

Temperature  of 
engine  room 
in°F. 

Temperature  of 
dynamo  bearing 
in°F. 

Frictional  rise 
in  temperature 
in°F. 

9.45  a.m. 

60 

120 

60 

10.0    a.m. 

61 

121 

60 

10.30  a.m. 

62 

121 

59 

11.0    a.m. 

Change  made  to  low  viscosity  oil. 

1.0    p.m. 

63 

99 

36 

1.30p.m. 

63 

97 

34 

2.0    p.m. 

62 

93 

31 

3.0    p.m. 

61 

90 

29 

4.0    p.m. 

59 

88 

29 

It  sometimes  takes  several  weeks  before  the  minimum  tem- 
perature is  reached,  especially  when  there  is  a  great  difference 
between  the  two  oils. 

Special  thermometers  are  used  for  taking  spindle  rail  tem- 
peratures; one  method  is  to  fix  a  shallow  box  to  the  rail;  the 
bottom  of  the  box  near  the  rail  has  a  long  slit  into  which 
the  thermometer  is  fixed,  the  bulb  being  pressed  lightly  against 
the  rail;  the  box  has  a  hinged  lid,  which  is  lifted  only  long  enough 
for  the  temperature  to  be  read. 

Temperature  tests  are  extremely  useful  for  comparing  oils 
in  actual  use,  and  the  tests  should  be  repeated  from  time  to  time 
with  a  view  to  checking  the  quality  of  the  oils  in  use.  If  the 
mechanical  conditions  do  not  change,  the  rise  in  temperature 
of  the  bearings  above  the  surrounding  air  should  remain  very 
nearly  constant. 

In  order  that  reliable  temperature  readings  may  be  taken,  quick 
registering  and  accurate  thermometers  should  be  used.  Most 
engineers'  thermometers  are  sluggish  and  liable  to  be  fractured 


74 


PRACTICE  OF  LUBRICATION 


when  carried  in  the  pocket  or  dropped  to  the  ground.  The 
author's  staff  of  engineers  broke  so  many  thermometers  of  the 
type  illustrated  in  Fig.  6  that  he  designed  a  special  thermometer 
and  case,  as  shown  in  Fig.  7.  The  thermometer  head  is  flexibly 
secured  in  the  cap,  which  fits  into  the  case  with  a  bayonet  joint, 
and  when  in  position  the  bulb  of  the  thermometer  is  kept  central 
out  of  contact  with  the  case  by  means  of  a  spring  pad.  When 
the  thermometer  is  carried  in  the  pocket,  it  cannot  be  broken, 
and  it  is  prevented  from  dropping  out  by  the  safety  pin  fastened 


FIG.  6. — Engineer's 
thermometer. 


FIG.  7. — Thomson's  engineer's 
thermometer. 


to  the  clothing.     The  introduction  of  this  thermometer  reduced 
the  number  of  breakages  practically  to  nil. 

Dynamometer  Tests.— Several  dynamometers,  such  as  Emer- 
son's and  Bailey's  dynamometers,  are  employed  for  measuring 
the  power  consumed  by  individual  machines,  such  as  spinning 
frames,  but  only  for  small  horse  powers. 

Emerson's  machine  (Fig.  8)  is  the  first  instrument  that  was 
ever  used  in  the  oil  business  for  the  purpose  of  showing  the  value 


TESTING  LUBRICANTS 


75 


of  good  lubrication.  It  is  fixed  to  the  driving  shaft  outside  the 
loose  pulley.  The  pull  of  the  belt  goes  through  the  arms  which 
pull  back  levers,  just  like  an  ordinary  weighing  scale,  and  the 
pointer  shows  the  number  of  pounds  exerted.  The  diameter  of 


FIG.  8. — -Emerson's  dynamometer. 


the  wheel  is  two  feet.     The  speed  is  measured  in  r.p.m.  and 
the  H.P.  is  calculated  from  the  formula: 

„  p        Net  weight  X  2  X  R.P.M. 
""33,000 

These  instruments  are  so  finely  adjusted  that  if  two  or  three 
spindles  are  stopped  by  hand,  the  pointer  immediately  registers 
the  increased  friction. 

Electrical  Tests. — Where  a  machine  or  a  group  of  machines  is 
driven  by  electric  motors,  it  is  a  simple  matter  to  record  the 
power  consumption.  But  apart  from  the  electrical  measure- 
ments (volts,  amperes,  k.w.  or  B.T.U.'s  per  hour,  as  the  case 
may  be )  it  is  desirable  or  necessary  to  record,  as  with  the  spinning 
frame  tests,  the  temperature  and* relative  humidity  of  the  air, 


76  PRACTICE  OF  LUBRICATION 

the  speeds  of  motor,  shafting  and  machines,  and  the  frictional 
temperatures  of  important  bearings,  all  with  a  view  to  getting 
as  complete  indications  as  possible  of  the  alterations  caused  by  a 
change  in  lubricants  or  lubricating  methods. 

Steam  Engine  Tests. — To  record  the  power  consumption  of  a 
factory  or  mill  by  means  of  indicator  diagrams  taken  from  the 
engine  requires  extreme  care  for  the  purpose  of  making  a  compari- 
son between  two  sets  of  lubricating  conditions.  The  load  always 
varies,  even  under  ihe  most  ideal  conditions;  the  governor  is 
continuously  altering  the  amount  of  steam  admitted,  and  dia- 
grams taken  quickly  after  one  another  may  differ  appreciably. 

The  only  accurate  method  is  to  take  a  great  number  of  indica- 
tor diagrams  (preferably  on  Tuesdays,  Wednesdays  or  Thursdays) 
at  regular  working  intervals,  say,  every  10  or  15  minutes  during, 
say,  4  working  hours;  the  indicator  pencil  motions  may  be  fitted 
with  magnets,  so  that  by  the  closing  of  a  switch,  all  diagrams 
can  be  taken  simultaneously. 

An  accurate  note  must  be  made  of  machines  stopped  in  the 
mill;  if,  for  example,  a  machine  consuming  8  H.P.  is  stopped  for 
half  an  hour,  the  equilavent  value  over  the  4  hours  is  1  H.P. 
If  the  values  of  all  such  stoppages  are  added  together  and  amount 
to  17  H.P.,  and  the  average  indicated  horse  power,  calculated 
from  all  diagrams,  is  805  H.P.,  then  it  may  be  assumed  that  the 
mill  would  consume  an  average  of  822  H.P.  if  all  the  machines  had 
been  working  continuously. 

If  on  the  comparative  test,  say,  3  months  later,  the  average 
power  with  other  oils  works  out  at  742  H.P.  and  the  value  for 
machines  stopped  is  14  H.P.,  then  the  comparative  power  value 
with  the  new  oils  is  754  H.P.,  which  represents  a  saving  of  68 
H.P.,  assuming  that  the  conditions  as  regards  temperature, 
relative  humidity,  etc.,  are  similar. 

Gas  Engine  Tests.— The  usual  particulars  should  be  recorded; 
the  gas  consumption  can  be  taken  when  a  gas  meter  is  installed, 
and  should  be  reduced  to  a  basis  of  32°F.  gas  temperature,  and 
28"  mercury  barometric  pressure,  so  that  the  amounts  of  gas 
consumed  on  both  tests  may  be  made  comparable.  The  tem- 
perature and  pressure  of  the  gas  should  therefore  be  recorded, 
also  the  calorific  value  of  the  gas.  The  temperature  of  water 
inlet  and  outlet  for  the  water  jacket,  temperature  of  intake  air, 
the  position  of  air  intake  on  engine  (if  variable),  and  the  number 
of  actual  explosions  per  minute  should  be  recorded  as  they 
may  prove  important  in  comparing  the  results  of  two  sets  of 
oils. 

Where   the   gas  consumption  cannot  be  recorded,  indicator 


TESTING  LUBRICANTS  77 

diagrams  may  be  taken,  from  which  the  power  consumption  can 
be  calculated. 

"Free  Revolution"  Tests. — An  approximate  comparison 
between  two  sets  of  lubrication  conditions  may  be  made  by  run- 
ning a  number  of  transmission  shafting,  counter  shafting,  and 
machines  idle  at  normal  speed,  and  then  suddenly  shutting  off 
steam,  gas,  electricity  or  whatever  moving  power  is  employed. 
The  prime  mover  (steam  engine,  gas  engine,  electric  motor,  etc.) 
will  continue  to  operate  for  a  certain  number  of  revolutions  and 
for  a  certain  length  of  time.  By  improving  the  lubrication,  the 
prime  mover  will  run  for  a  longer  period  and  a  greater  number  of 
"free  revolutions"  before  it  comes  to  a  standstill.  This  method 
is  not  very  scientific,  but  is  simple  to  carry  out  and  often  very 
useful. 

Similar  effects  are  noticed  on  spinning  frames;  with  improved 
lubrication  they  run  for  a  longer  time  when  the  belts  are  thrown 
on  to  the  loose  pulleys.  In  the  same  way,  the  driver  of  a  hoisting 
engine  finds  that  he  opens  his  throttle  later  and  closes  it  earlier 
when  the  lubrication  of  valves  and  cylinders  is  improved.  It 
will  generally  be  found  that  engine  attendants  or  machine  opera- 
tors who  have  handled  their  machines  for  a  long  time  have  some 
way  of  judging  the  state  of  lubrication  efficiency.  They  know 
at  once  if  there  is  a  change,  although  many  of  them  do  not 
know  how  to  express  themselves  in  technical  terms. 

General  Remarks.  --As  to  selecting  a  suitable  part  of  a  factory 
for  a  test,  it  is  difficult  to  give  general  rules.  It  will  often  be 
found  that  ohe  engineer  of  an  up-to-date  works  has  a  favorite 
piece  of  plant  on  which  he  makes  all  his  trials  and  tests.  Such 
a  plant  should  always  be  given  preference,  providing  of  course 
that  it  meets  all  requirements,  as  he  will  be  more  familiar  with 
the  running  of  such  machinery,  and  will  the  more  readily  notice 
any  improvement  achieved  by  changing  the  lubricant. 

Where  it  is  possible  a  compact  group  of  machines  should  be 
chosen.  It  is  desirable  that  the  group  be  compact,  so  that  the 
whole  of  the  plant  may  be  under  observation  of  the  operator 
while  running;  the  stoppage  of  a  machine,  the  breaking  of  a  belt, 
or  the  heating  of  a  bearing,  can  be  seen  at  once,  a  note  made  of 
the  time  the  machine  is  put  out  of  action,  and  allowance  made 
for  it  in  the  final  results. 

It  must  not  be  forgotten  that  a  considerable  time  must  usually 
be  allowed  between  two  comparative  tests,  to  ensure  that  condi- 
tions with  the  new  lubricants  in  use  have  become  uniform. 
Where  speeds  are  high  and  both  sets  of  oils  are  pure  mineral  in 
character,  a  few  weeks  will  be  sufficient;  but  where  speeds  are 


78  PRACTICE  OF  LUBRICATION 

lower  and  pressures  heavier,  and  particularly  if  the  oils  in  the  first 
set  are  compounded  and  in  the  second  set  straight  mineral,  or  if 
there  is  a  great  difference  in  viscosities,  the  author  has  found  that 
the  change  in  power  consumption  may  easily  take  three  months 
to  be  fully  accomplished. 


CHAPTER  VI 
THE  LAWS  OF  FRICTION 

Without  friction,  life  in  the  various  forms  in  which  we  are 
acquainted  with  it  would  exist  only  for  a  very  short  time.  Any 
moving  mass  would  retain  and  continue  its  motion.  If  it  were 
sliding  down  an  incline  and  accelerating,  it  would  reach  another 
incline  and  rise  to  a  certain  height,  then  move  to  another  position 
at  the  same  height  above  sea  level,  and  continue  without  ever 
coming  to  rest. 

Everything  except  the  solid  rocky  formations  would  start  slid- 
ing. Towns  and  cities  would  be  swept  away  with  the  country; 
steamers  on  the  open  sea,  at  the  moment  friction  ceased  to  be, 
would  not  be  able  to  accelerate  or  decrease  their  speed,  as  the  fric- 
tion between  the  propeller  and  the  water  and  bet  ween  the  particles 
of  water  themselves  would  be  non-existent.  Sailing  ships  would 
be  in  the  same  plight,  as  the  wind  would  have  no  effect  on  the 
sails.  Locomotives  would  not  be  able  to  move,  as  there  would  be 
no  rail  friction. 

Friction  can  be  defined  as  the  resistance  created  by  the  surface 
of  one  body  moving  over  the  surface  of  another.  If  no  lubricant 
is  introduced  between  the  surfaces,  the  friction  is  what  may  be 
termed  solid  friction.  If  there  were  nothing  but  solid  friction, 
very  little  machinery  could  be  kept  in  operation,  fast-going 
steamers  and  railway  expresses  would  be  unknown,  and  only  the 
crudest  forms  of  slow-running  machinery  could  be  operated. 

Solid  Friction/ — All  surfaces  are  more  or  less  rough;  even  sur- 
faces which  are  well  machined  and  polished  show  under  the  micro- 
scope small  projections  and  depressions.  It  is  the  interlocking 
of  these  minute  projections  which  causes  Solid  Friction  when  two 
unlubricated  surfaces  are  pressed  together  and  move  relative  to 
one  another. 

When  the  rubbing  surfaces  are  very  smooth  and  in  intimate 
contact  an  additional  resistance  to  motion  may  be  created  by  ad- 
hesion between  the  surfaces  caused  by  molecular  attraction. 
This  adhesive  force  is  shown  by  Johnson's  Swedish  limit  gages  used 
in  many  engineering  works.  When  two  or  more  of  these  gages 
are  brought  into  close  contact,  they  adhere  with  a  force  several 
times  that  of  the  atmospheric  pressure,  and  it  i&  difficult  to  slide 

79 


80  PRACTICE  OF  LUBRICATION 

one  surface  over  another,  notwithstanding  the  absence  of  ex- 
ternal pressure.  It  is  only  in  very  rare  cases,  with  surfaces  which 
fit  exceedingly  well,  that  this  adhesive  force  makes  itself  felt. 
Speaking  generally,  the  laws  of  solid  friction  are  as  follows: 
The  frictional  resistance  with  solid  friction  is 

(a)  directly  proportional  to  the  total  pressure  between  the  surfaces; 
(6)  independent  of  the  rubbing  speed  of  the  surfaces,  at  low  speeds,  but 
decreases  at  very  high  speeds; 

(c)  independent  of  the  areas  of  the  surfaces; 

(d)  dependent  to  a  considerable  extent  on  the  roughness  and  hardness 
of  the  surfaces. 

These  laws  apply  whether  the  motion  is  rolling  or  sliding;  they 
apply  therefore  to  ball  and  roller  bearings. 

That  the  friction  decreases  at  high  speeds  is  well  illustrated  by 
the  greatly  diminished  brake-effect  of  automobile  brakes  at  very 
high  speeds.  The  action  of  the  brakes  may  become  so  reduced 
that  it  may  not  be  possible  to  regain  control  of  the  car  when  going 
down  a  steep  hill. 

Contaminated.  Surf  aces. — It  is  an  important  fact  that  surfaces 
are  never  perfectly  clean.  Chemically  clean  surfaces  soon  abrade 
and  weld  themselves  together,  when  rubbing  over  one  another; 
fortunately,  all  surfaces  are  covered  with  what  may  be  called 
contamination  films  of  a  more  or  less  greasy  nature;  these  films 
are  due  to  the  action  of  air,  moisture,  dust  and  impurities  on  the 
surfaces,  and  they  help  to  some  extent  in  preventing  abrasion, 
at  any  rate  under  low  pressure  conditions;  in  fact,  they  act  very 
much  like  thin  lubricating  films.  Archbutt  and  Deeley  mention 
the  following  experiment  to  illustrate  the  effect  of  contamination. 

"A  smooth  file  passed  over  a  freshly  prepared  clean  surface  will  be 
found  to  cut  well  even  when  only  gently  pressed  against  the  metal; 
but  if  the  hand  be  passed  over  the  metallic  surface,  the  film  of  grease 
therefore  deposited  will  so  lubricate  it,  that  considerably  greater  pressure 
on  the  file  is  now  needed  to  cause  it  to  cut." 

Owing  to  the  surface  irregularities  of  the  rubbing  surfaces 
wear  takes  place,  the  softer  surface  being  more  rapidly  abraded 
than  the  harder.  The  wear  and  friction  are  much  less  for  hard 
and  smooth  surfaces  than  for  soft  and  rough  surfaces.  .  ; 

Surfaces  of  exactly  the  same  material  are  more  inclined  to  seize 
and  weld  than  dissimilar  surfaces;  hence  the  reason  why  materials 
of  different  hardness  and  composition  are  used  for  all  rubbing 
surfaces,  as  for  example,  a  steel  journal  in  a  white-metalled 
bearing,  soft  cast-iron-  piston  rings  against  a  harder  cast-iron 
cylinder,  etc. 


THE  LAWS  OF  FRICTION  81 

Although  the  friction  between  solid  surfaces  is  independent  of 
the  area  in  contact,  the  wear  is  obviously  the  greater  the  smaller 
the  area  because  of  the  greater  pressure  per  square  inch. 

By  the  introduction  of  a  suitable  third  medium  between  the 
frictional  surfaces,  which  medium  may  be  solid  (such  as  graphite, 
talc,  white-lead  and  the  like),  or  of  an  oily  nature  (such  as  lubri- 
cating grease  or  lubricating  oils),  the  solid  friction  may  be  par- 
tially or  wholly  eliminated,  and,  with  the  latter  mentioned  mediae, 
replaced  with  soft — solid  or  fluid  friction.  Roller  bearings  and 
ball  bearings  are  excepted  in  this  connection. 

Fluid  Friction. — The  object  of  all  lubrication  is  that  the  lubri- 
cant should  attach  itself  to  the  rubbing  surfaces,  and  form  a 
film  between  them,  which  under  the  conditions  of  speed,  pressure 
and  temperature  prevailing  will  not  be  squeezed  out,  but  will 
keep  the  frictional  surfaces  apart.  This  object  is  not  often 
attained,  except  in  high  speed  bearings,  as  for  example,  stream-fed 
bearings  lubricated  by  a  circulation  oiling  system  as  in  steam 
turbines  and  high  speed  steam  engines,  many  ring  oiling  bearings, 
Michell  bearings,  etc. 

In  bearings  thus  perfectly  lubricated  the  "rubbing"  surfaces 
never  touch  one  another  and  the  friction  is  entirely  dependent  on 
the  lubricant.  The  laws  governing  fluid  friction  are  totally 
different  from  the  laws  for  solid  friction,  and  may  be  summarized 
as  follows: 

The  frictional  resistance  with  fluid  friction 

(a)  is  independent  of  the  pressure  between  the  surfaces; 

(6)  increases  with  speed  of  rubbing  surfaces; 

(c)  increases  with  area  of  rubbing  surfaces; 

(rf)  is  independent  of  the  condition  of  the  rubbing  surfaces,  or  the  ma- 
terials of  which  they  are  composed. 

(e)  depends  entirely  on  the  viscosity  of  the  lubricant  at  the  working 
temperature  of  the  oil  film. 

If  the  frictional  resistance  is  F  and  the  total  pressure  between 
the  rubbing  surfaces  P,  then  the  friction  equals  P  multiplied  by 
the  coefficient  of  friction  C,  i.e.: 

F  =  C  XP 

F 
and:  C  —  p 

The  coefficient  of  friction  for  unlubricated  surfaces  ranges 
from  0.1  to  0.4,  but  with  fluid  friction  the  coefficient  of  friction 
ranges  from  0.002  to  0.01  according  to  the  viscosity  of  the  oil. 
It  is  therefore  worth  while,  wherever  possible,  to  design  bearings 
so  that  fluid  friction,  or  a  condition  approaching  fluid  friction,  can 
be  brought  about. 


82 


PRACTICE  OF  LUBRICATION 


For  journal  bearings  a  formula  is  mentioned,  page  105,  indi- 
cating a  relation  between  pressure  and  surface  speed,  which 
ensures  fluid  friction. 

Michell  obtains  fluid  friction  in  his  design  of  thrust  bearing  by 
means  of  self-adjusting,  tilting  bearing  blocks. 

Semi-lubricated  Surfaces. — Under  conditions  of  low  speed 
and  high  pressure  it  is  impossible  or  extremely  difficult  to  obtain 
pefect  film  formation,  nor  is  it  possible  in  the  great  majority  of 
bearings,  which  are  not  stream-fed  but  only  supplied  with  a 
limited  amount  of  oil  per  minute,'  to  produce  anything  approach- 
ing perfect  film  formation.  The  surfaces  accordingly  are  in  an 
imperfectly  lubricated  or  semi-lubricated  condition,  for  which 
the  coefficient  of  friction  will  range  from  0.01  to  0.10  according  to 
whether  the  surfaces  are  very  poorly  lubricated — approaching 
the  condition  of  unlubricated  surfaces,  or  fairly  well  lubricated — 
approaching  the  condition  of  perfectly  lubricated  surfaces. 

There  are  no  Definite  Laws  Governing  the  Lubrication  of  Semi- 
lubricated  Surfaces. — The  frictional  resistance  is  composed 
partly  of  solid  friction  and  partly  of  fluid  friction,  and  the  more 
the  solid  friction  predominates,  the  more  important  is  the  prop- 
erty known  as  oiliness,  and  the  less  important  the  viscosity  of 
the  lubricant.  The  object  of  lubrication  of  such  surfaces  is  to 
make  the  best  possible  compromise  between  reduction  of  wear 
and  reduction  of  fluid  friction.  For  conditions  of  low  pressure 
and  high  speed,  the  reduction  of  fluid  friction  is  usually  the  most 
important  point  to  consider  and  demands  low  viscosity  oils  of 
great  oiliness;  whereas  for  conditions  of  high  pressure  and  low 
speed,  the  reduction  of  wear  must  be  given  prime  consideration 
and  therefore  calls  for  viscous  oils,  of  great  oiliness. 

In  ball  and  roller  bearings  the  friction  is  usually  not  influenced 
by  lubrication  and  is  lower  than  the  friction  in  even  the  best 
lubricated  plain  bearings. 

Below  is  given  approximate  values  for  the  coefficient  of  fric- 
tion for  the  sake  of  comparison. 


Condition  of  surfaces 

Coefficient  of  friction 

Range 

Average  value 

Unlubricated  or  very  poorly  lubricated  surfaces  . 
Semi-lubricated  surfaces  .  . 

.1      to  .4 
.01    to  .10 
.002  to  .01 

.001  to  .003 
.002  to  .007 

.16 
.03 
.006 

.002 
.005 

Perfectly  lubricated  surfaces  .  . 

Surfaces  in  rolling  contact  : 
Ball  bearings  .... 

Roller  bearings  

THE  LAWS  OF  FRICTION  83 

The  author  does  not  propose  in  this  book  to  go  into  greater 
detail  as  to  the  range  in  value  of  the  coefficient  of  friction  for 
particular  types  of  surfaces,  or  the  variations  brought  about  by 
alterations  in  speed,  pressure,  temperature,  method  of  applica- 
tion, etc. 

The  practical  aspect  of  the  case  will  gradually  emerge  and  pre- 
sent itself  in  the  various  chapters;  the  theoretical  aspect  of 
lubrication  would  be  best  treated  in  a  volume  by  itself  in  order 
to  do  full  justice  to  such  an  important  subject. 

Static  Coefficient  of  Friction. — The  values  given  above  for  the 
coefficient  of  friction  are  the  kinetic  values,  applying  to  surfaces 
in  motion.  When  surfaces  have  been  at  rest  for  some  time  the 
oil  film  is  more  or  less  completely  squeezed  out  and  a  certain 
amount  of  metallic  contact  takes  place.  As  a  result,  the  start- 
ing effort,  when  the  surfaces  are  again  brought  into  motion,  is 
much  greater  than  the  running  effort;  in  fact,  the  static  coefficient 
of  friction  usually  approximates  the  values  for  solid  friction. 

When  the  speed  of  the  rubbing  surfaces  is  very  low,  the  kinetic 
coefficient  of  friction  may  be  even  higher  than  the  static  value, 
as  there  is  added  to  the  solid  friction  the  resistance  caused  by 
the  presence  of  a  lubricant,  it  being  understood  that  the  speed  of 
rubbing  is  too  low  to  allow  the  lubricant  to  produce  any  appre- 
ciable separation  of  the  rubbing  surfaces.  As  the  speed  in- 
creases and  the  lubricant  begins  to  produce  a  film,  the  solid 
friction  quickly  decreases  and  the  kinetic  coefficient  of  friction 
is  likewise  reduced,  until  perfect  film  formation  is  brought 
about. 

The  high  values  for  the  static  coefficient  of  friction  explain 
the  great  effort  often  required  to  start  engines  or  machinery  from 
rest,  and  form  one  of  the  chief  reasons  why  ball  and  roller  bearings 
are  used,  as  with  surfaces  in  rolling  contact  there  is  practically 
no  difference  between  the  static  and  the  kinetic  coefficient  of 
friction. 

The  static  coefficient  of  friction  will  obviously  depend  on: 

1.  The  condition  and  hardness  of  the  surfaces;  it  being  lower  for  hard  and 
smooth  surfaces  than  for  soft  and  rough  surfaces. 

2.  The  pressure  between  the  surfaces;  the  greater  the  pressure,  the  more 
effectively  is  the  lubricant  squeezed  out. 

3.  The  length  of  time  the  surfaces  have  been  at  rest;  the  longer  the  time  the 
greater  chance  has  the  pressure  of  displacing  the  lubricant. 

4.  The  nature  of  the  lubricant. 

Solid  lubricants  like  graphite  are  not  displaced,  so  that  in 
bearings  lubricated  entirely  by  solid  lubricants  the  static  and 
kinetic  coefficients  of  friction  (within  resonable  limits)  are  very 


84  PRACTICE  OF  LUBRICATION 

similar.  Semi-solid  lubricants  cannot  be  entirely  displaced  by 
pressure  during  a  period  of  rest;  this  is  an  advantage  as  compared 
with  oils  which  occasionally  may  be  of  importance.  Mineral 
oils  are  almost  completely  displaced,  but  experience  proves  that 
fixed  oils,  or  mineral  oils  compounded  with  fixed  oil,  leave  a 
better  film  in  between  the  surfaces,  and  that  therefore  the  static 
coefficient  of  friction  with  the  latter  oils  is  considerably  less  than 
with  straight  mineral  oils.  As  a  result,  not  only  is  the  starting 
effort  reduced,  but  also  the  wear  caused  by  metallic  abrasion 
during  the  initial  moments  of  starting. 


CHAPTER  VII 
LUBRICATING  APPLIANCES 

The  main  types  of  lubricators  and  lubricating  appliances  are 
described  under  "Bearings."  It  will  carry  the  author  too  far  to 
elaborate  further  on  the  many  types  and  constructions  of  lubri- 
cators in  existence;  he  hopes  that  sufficient  is  said  under  " Bear- 
ings" to  convey  his  views  on  the  merits  or  demerits  of  the 
various  principles  involved. 

As,  however,  mechanically  operated  lubricators  are  coming 
much  into  prominence,  and  as  the  author  has  taken  a  particular 
interest  in  these  appliances,  he  feels  that  a  critical  review  of  the 
main  types  may  prove  useful. 

Mechanically  operated  lubricators  are  now  widely  used  for 
delivering  a  small  or  moderate  supply  of  oil  automatically  and 
at  a  uniform  rate  of  feeding,  against  a  pressure  ranging  from  a 
few  pounds  to  as  much  as  1,000  Ib.  per  sq.  in. 

Mechanical  lubricators  are  used  for  feeding  oil  to  the  cylinders 
and  valves  of  steam  engines,  and  air  compressors,  the  cylinders 
and  bearings  of  gas  engines,  kerosene  engines,  semi-Diesel  engines, 
Diesel  engines,  the  piston  rod  glands  of  certain  ammonia  com- 
pressors, certain  large  and  important  bearings,  which  for  some 
reason  or  other  must  have  the  oil  forced  in  under  pressure  to 
prevent  wear,  etc. 

In  order  to  analyze  the  merits  or  demerits  of  the  very  numerous 
types  of  mechanically  operated  lubricators,  some  of  the  im- 
portant features  will  be  discussed  as  follows: 

SIGHT  FEEDS 

PUMP  PLUNGERS 

VALV  ES 

TYPES  OF  DRIVE 

FEED  ADJUSTMENT 

STRAINER 

CHECK  VALVES. 

Sight  Feeds. — From  this  point  of  view,  mechanically  operated 
lubricators  may  be  classified  as  follows: 

Mechanically  operated  lubricators  without  sight  feeds. 

Mechanically  operated  lubricators  with  sight  feeds  on  the  suc- 
tion side  of  the_pumps. 

85 


80  PRACTICE  OF  LUBRICATION 

Mechanically  operated  lubricators  with  sight  feeds  on  the  dis- 
charge side  of  the  pumps. 

Mechanically  Operated  Lubricators  Without  Sight  Feeds. — The 
Mollerup  (so  called  after  the  inventor,  a  Danish  engineer)  me- 
chanically operated  lubricator  is  the  most  widely  used  lubricator 
of  this  type  in  Europe.  A  large-diameter  plunger  is  slowly  forced 
into  a  cylinder  filled  with  oil  by  means  of  a  ratchet  actuating 
motion  combined  with  a  worm  gear  drive.  The  oil  thus  driven 
out  is  passed  through  piping  to  the  engine. 

When  the  lubricator  is  being  filled,  air  may  be  drawn  into  the 
cylinder,  so  that  the  lubricator  does  not  start  feeding  immediately 
the  engine  starts,  and  lubrication  difficulties  may  therefore  arise 
before  the  lubricator  commences  to  discharge  the  oil. 

Due  to  the  absence  of  sight  feeds,  irregular  working  of  these 
lubricators,  such  as  leakage  past  the  pump  plunger,  is  not  al- 
ways observed  in  time  to  prevent  trouble. 

Some  American  mechanically  operated  lubricators  have  oil 
blinkers  in  the  discharge  line  which  act  as  the  equivalent  of 
sight  feeds;  they  blink  every  time  oil  is  forced  through,  but  do 
not  indicate  the  actual  amount  of  oil  passing. 

Other  makers  put  two-way  lest  cocks  in  the  delivery  pipes. 
When  the  handle  of  these  cocks  is  turned  to  a  horizontal  position, 
the  oil  is  delivered  out  through  a  test  pipe  into  the  atmosphere 
under  no  pressure;  it  is  assumed  that  when  the  handle  is  turned 
vertical,  the  same  amount  of  oil  will  be  fed  to  the  engine  against 
pressure.  If,  however,  the  pump  is  not  efficient  or  if  it  is  out  of 
order,  this  will  not  be  the  case;  less  oil  will  be  forced  to  the  engine 
than  is  indicated  by  the  test  cock. 

In  a  multiple  feed,  mechanically  operated  lubricator  of  this 
type,  if  one  feed  is  choked  and  the  other  feeds  are  working 
normally  it  is  impossible  to  locate  the  defective  pump  until  the 
part  of  the  engine  supplied  gives  clear  evidence  of  the  lack  of 
lubrication. 

Mechanically  Operated  Lubricators  with  Sight  Feeds  on  the  Suction 
Side  of  the  Pumps. — Some  mechanically  operated  lubricators  of 
this  type  (Fig.  9)  have  a  container  from  which  the  oil  is  fed  by 
gravity  through  sight  feeds;  the  oil  feeds  are  controlled  by  ad- 
justable needle  valves  and  whatever  oil  drops  into  the  pumps 
is  forced  to  the  engine,  less  possible  leakage  past  the  plungers. 

The  disadvantage  of  these  lubricators  is  that  the  oil  feeds 
irregularly,  due  to  variation  in  oil  level  and  oil  temperature. 
Furthermore,  dirt  is  liable  to  choke  up  the  needle  valves  and  cause 
erratic  oil  supply.  As  the  oil  feeds  are  started  and  stopped  by 
hand,  these  lubricators  are  not  entirely  automatic  in  action. 


LUBRICATING  APPLIANCES 


87 


Other  mechanically  operated  lubricators,  although  they  have 
the  sight  feeds  on  the  suction  side  of  the  pumps,  are  fully  auto- 
matic in  action,  the  oil  feeds  starting  and  stopping  with  the 
engine.  One  type  of  these  lubricators  (Fig.  10)  has  a  single 
plunger  which  on  the  suction  stroke  draws  oil  through  a  sight 
feed  glass  filled  with  water;  on  the  delivery  stroke  the  suction 
valve  closes  and  oil  is  forced  out  through  a  spring-loaded  delivery 
valve.  One  important  drawback  to  this  arrangement  is  that  the 
water  in  the  sight  feed  glass  gradually  disappears  and  is  replaced 


1  Driving  Cam 

2  Driving  Rocker 

3  Pump  Plunger 

4  Sight  Feed 

5  Oil  Discharge 
Pipe 


2-p> 


FIG.  9. — Mechanically  operated  lubricator  with  gravity  sight  feeds. 

by  oil;  this  occurs  even  if  a  suction  valve  be  placed  below  the  glass, 
as  it  cannot  be  spring  loaded;  the  author  can  see  no  virtue  in 
the  sight  feed  glass  not  being  under  pressure.  Sight  feed  glasses 
seldom  break  because  of  internal  pressure ;  they  are  either  knocked 
to  pieces  or  they  are  fractured  because  of  excessive  strains  set 
up  when  placing  them  in  position.  If  the  sight  feed  glass  is 
broken,  the  oil  feed  stops,  as  air  is  sucked  into  the  sight  feed  in 
place  of  oil. 

All  water-filled  sight  feed  glasses  are  liable  to  be  fractured  in 
the  cold,  if  the  water  freezes.  This  is  prevented  by  adding 
ordinary  salt'or  glycerine  to  the  water. 


88 


PRACTICE  OF  LUBRICATION 


With  most  lubricators,  which  have  the  sight  feed  arrangement 
on  the  suction  side  of  the  pumps,  one  cannot  be  certain  that  the 
true  oil  feed  is  shown.  If  the  pump  plunger  leaks  on  the  delivery 
stroke,  some  of  the  oil  will  leak  back  to  the  oil  container;  this  can- 
not easily  be  observed,  and  if  the  leakage  is  appreciable,  it  means 


FIG.  10. — Mechanically  operated  lubricator;  sight  feed  glass  on  suction  side. 

that  more  oil  passes  through  the  sight  feed  than  is  actually  dis- 
charged by  the  pump  to  the  engine. 

Some  lubricators  have  "  dummy  sight  feeds."  One  plunger 
pumps  the  oil  through  a  sight  feed,  while  a  similar  plunger 
pumps,  what  is  believed  and  hoped  to  be,  a  similar  amount  of  oil 


LUBRICATING  APPLIANCES  89 

to  the  engine;  the  oil  drops  through  the  sight  feed  back  to  the 
oil  container.  Cases  have  occurred  where  one  plunger  was  pump- 
ing oil  merrily  through  the  sight  feed  while  the  corresponding 
plunger  was  air  locked.  Strange  to  say,  thousands  of  such  lubri- 
cators have  been  sold  and  engineers  have  not  even  taken  the 
trouble  to  ascertain  whether  the  sight  feeds  were  true  sight  feeds 
or  were  merely  dummies. 

Several  types  of  lubricators  have  two  plungers  for  each  oil 
feed.  A  measuring  pump  draws  the  oil  from  the  container  and 
discharges  it  under  low  pressure  through  a  sight  feed,  whence 
it  is  sucked  into  the  delivery  pump  chamber  and  discharged 
through  a  check  valve  to  the  engine. 

Instead  of  two  separate  plungers,  a  two-diameter  plunger  is 
sometimes  used,  the  small  diameter  part  acting  as  the  discharge 
plunger.  If  there  be  any  leakage  from  the  discharge  plunger,  the 
oil  can  generally  be  seen  filling  up  in  the  sight  feed  and  steps 
can  be  taken  to  rectify  the  trouble.  With  a  two-diameter  plunger 
properly  constructed,  all  the  oil  passing  through  the  sight 
feed  is  forced  to  the  engine,  never  less,  as  with  leaky  single 
plungers. 

Mechanically  Operated  Lubricators  with  Sight  Feeds  on  the 
Discharge  Side  of  the  Pumps. — Sight  feeds  which  show  the  oil  in 
the  form  of  drops  rising  through  water  are  true  sight  feeds,  as 
they  show  the  oil  after  it  has  left  the  pump  and  is  actually  on 
its  way  to  the  engine;  it  cannot  go  anywhere  else. 

Figs.  11  and  12  show  a  cylindrical  sight  feed  glass  and  Fig. 
13  a  single  bulFs-eye  sight  feed  arrangement;  the  former  sight  feed 
will  stand  300-400  Ib.  and  the  latter  800-1,000  Ib.  per  sq. 
inch  quite  safely,  when  well  made. 

The  glass  in  Figs.  11  and  12  has  both  ends  rounded  and  ground 
by  a  circular  grinder,  so  that  there  are  no  sharp  edges,  whence 
fractures  might  emanate. 

In  a  dark  engine  room  it  may  be  difficult  to  see  the  oil  feed  in 
the  bull's-eye  shown  in  Fig.  13,  so  a  better  arrangement  is  to  have  a 
double  bull's-eye  with  glasses  both  front  and  back.  To  keep  the 
oil  drops  away  from  the  glass  it  is  good  practice  to  have  a  climb- 
ing wire  inserted  in  the  nozzle  from  above  (Fig*  11);  the  oil 
drops  form,  move  up  the  wire  and  unite  with  the  oil  at  the  top 
without  removing  any  water;  when  there  is  no  wire  (Fig.  12), 
the  drops  wobble  up  through  the  water  and  usually  lean  against 
a  corner,  each  drop  enclosing  and  carrying  away  with  it  a  small 
globule  of  water,  so  that  the  glass  soon  fills  up  with  oil;  this  is 
avoided  by  having  a  climbing  wire,  as  shown. 

Another  useful  feature  is  shown  in  the  shape  of  the  nozzle 


90 


PRACTICE  OF  LUBRICATION 


(Fig.  11),  this  being  narrow  below  the  head.  This  prevents  oil 
drops  from  sagging  and  creeping  down  the  side  of  the  nozzle 
and  smearing  the  sight  feed  glass,  as  in  Fig.  12. 

A  third  point  of  importance  for  keeping  the  water  in  the  glass 
is  a  spring  loaded  check  valve  below  the  nozzle;  if  this  valve  be  not 
loaded,  it  " floats"  after  the  delivery  stroke  has  been  completed, 
and  if  it  is  not  seated  at  the  beginning  of  the  suction  stroke  a  little 
water  may  be  sucked  into  the  mouth  of  the  nozzle;  the  result 
is  that  the  glass  slowly  fills  with  oil. 


FIGS.  11-12. — Sight  feed  glass  under  pressure. 

In  very  cold  weather  steam  cylinder  oil  becomes  very  sluggish ; 
the  oil  drops  become  bigger,  and  even  with  a  climbing  wire,  etc., 
the  drops  are  inclined  to  take  "pin  pricks"  of  water  away  with 
them  and  slowly  empty  the  glasses  of  water. 

If  the  pump  is  a  good  one  and  will  pump  water,  a  simple  way 
of  driving  out  accumulated  oil  from  a  sight  glass  and  replacing 
it  with  water  is  to  pour  a  small  quantity  of  water  into  the  lubri- 
cator container  gradually,  until  the  water  begins  to  make  its  ap- 
pearance at  the  sight  feed  nipple  in  place  of  oil.  Then  add  a 
little  more,  say  an  egg-cupful  or  what  seems  necessary,  and  the 
water  will  be  pumped  up  by  the  action  of  the  lubricator,  refilling 
the  glass  and  driving  the  oil  out.  If  the  engine  can  be  stopped 


LUBRICATING  APPLIANCES 


91 


the  proper  method  is  to  uncouple  and  clean  the  glass,  and  fill  up 
in  the  usual  way.  The  method  described  is,  however,  useful 
where  an  engine  runs  continuously. 

Many  engineers  appear  to  be  under  the  impression  that  a 
mechanical  lubricator  pumps  oil  only  when  a  drop  rises  in  the 
sight  feed  glass.  This  is,  of  course,  erroneous.  Let  us  assume 
that  it  takes  ten  strokes  of  the  pump  for  one  drop  to  rise  through 
the  glass;  then  for  every  stroke  of  the  pump,  the  drop  forming 
on  the  nozzle  grows  in  size  with  a  quantity  equal  to  one-tenth 
of  a  drop,  but  as  the  glass  is  full  of  water  and  the  oil  pipe  leading 


TIG.   13. — Mechanically  operated  lubricator  with  bull's-eye  sight  feed. 

to  the  engine  completely  filled  with  oil  right  to  the  check  valve 
fitted  at  its  extreme  end,  it  must  be  clear  that  for  every  stroke 
of  the -pump  one-tenth  of  a  drop  is  forced  into  the  sight  glass 
at  the  nozzle  and'one-tenth  of  a  drop  is  simultaneously  discharged 
at  the  other  end  through  the  check  valve.  When  the  pump  has 
made  ten  strokes,  the  drop  of  oil  formed  on  the  nozzle  becomes 
sufficiently  large  to  overcome  by  its  floating  power  its  adhesion 
to  the  nozzle;  the  drop  then  rises,  which  simply  means  that 
it  changes  its  position  in  the  sight  feed  glass,  moving  from 
the  nozzle -up  to  the  top  of  the  glass;  this  movement  does  not 


92  PRACTICE  OF  LUBRICATION 

in  any  way  affect  the  discharge  of  oil  from  the  check  valve  end 
of  the  oil  pipe,  which  continues  to  be  one-tenth  of  a  drop  every 
time  the  pump  plunger  completes  its  delivery  stroke. 

Pump  Plungers. — These  should  not  be  too  large  in  diameter, 
as  then  the  pump  strokes  have  to  be  very  short  and  easily  be- 
come irregular.  Two-diameter  plungers  are  advantageous,  as  the 
difference  between  the  two  diameters  (see  Fig.  13)  can  be  made 
very  small,  say  ^4"  (Y±'  X  1%4/');  if  the  plungers  have  to 
operate  at  high  speed  and  must  only  supply  a  small  amount  of 
oil  (Diesel  engine  cylinders,  for  example)  the  stroke  will  still 
be  perceptible,  whereas  with  single  plungers,  %  inch  diameter, 
it  would  be  well  nigh  impossible  to  adjust  the  stroke  to  the  re- 
quired length  and  maintain  it  with  certainty. 

Pump  plungers  should  preferably  not  operate  vertically 
with  the  oil  below  them,  as  they  then  easily  become  air  locked, 
and  it  is  difficult  to  let  the  air  out.  Plungers  should  either 
operate  horizontally  or,  if  vertical,  should  have  the  oil  above  the 
plunger  discharge  end. 

Outside  plungers  with  packings  should  be  avoided,  as,  if 
the  plungers  get  scored,  the  leakage  is  difficult  to  overcome. 
It  is  better  to  have  plungers  inside  the  oil  container  and  sealed 
by  the  oil;  if  the  plungers  are  hardened  and  ground  to  a  good 
sliding  fit,  they  will  pump  against  considerable  pressure  with 
no  or  only  slight  leakage. 

It  is  bad  practice  to  have  two  horizontal  plungers  operating 
together  on  opposite  sides  of  the  container  and  firmly  connected; 
it  means  that  when  they  are  a  good  fit,  it  takes  great  force  to 
move  them,  it  being  impossible  to  drill  the  pump  cylinders  in 
perfect  alignment.  Such  a  plunger  arrangement  causes  exces- 
sive strain  and  wear  of  the  driving  mechanism. 

Valves. — Most  lubricators  have  single  suction  and  delivery 
valves.  If  a  valve  becomes  inactive  by  a  piece  of  dirt  getting 
on  to  the  valve  seat,  the  lubricator  may  stop  feeding.  The 
author  strongly  recommends  two  suction  and  two  delivery  valves, 
so  that  one  valve  will  act  while  the  other  valve  is  given  a  chance 
to  get  free  of  the  dirt.  The  second  delivery  valve  should  be 
spring  loaded  to  secure  prompt  closing.  Spring  loaded  suction 
valves  are  unsatisfactory,  as  the  springs  have  to  be  very  weak 
indeed,  if  they  are  not  to  interfere  with  the  pump  action  on  the 
suction  stroke. 

The  valves  should  be  easily  accessible,  the  suction  valves  in 
particular.  Fig.  13  shows  one  method  of  placing  the  suction 
valves  in  a  detachable  cage.  The  pump  should  preferably 
be  capable  of  freeing  itself  from  air.  With  a  spring  loaded 


LUBRICATING  APPLIANCES  93 

delivery  valve  it  becomes  necessary  to  let  the  air  out,  in  case  of  an 
air  lock;  this  may  be  done  as  shown  in  Fig.  13  by  having  a  small 
air  vent  between  the  two  delivery  valves.  This  is  opened, 
until  all  air  is  driven  out  and  oil  appears  at  the  vent;  it  is  then 
closed  and  the  oil  having  already  passed  the  bottom  valve  will 
force  open  the  top  valve. 

Some  pumps  do  not  have  suction  valves,  but  suction  ports, 
which  are  uncovered  and  closed  by  the  movement  of  the  plunger. 
A  complete  vacuum  is  created  on  the  suction  stroke,  and  when  the 
suction  port  is  uncovered  oil  is  sucked  in;  but  with  viscous 
oils  like  steam  cylinder  oils,  the  pump  motion  must  be  very  slow, 
to  ensure  that  the  pump  draws  in  a  full  charge  of  oil.  A  few 
lubricators  have  no  valves  at  all,  but  control  the  oil  inlets 
and  outlets  by  plungers  very  much  like  a  piston  valve  arrange- 
ment in  steam  engines;  this  arrangement  requires  most  excellent 
and  accurate  workmanship  to  give  satisfaction  for  high  pressure 
conditions.  Whatever  the  valve  arrangement  may  be,  it  is 
always  desirable  that  the  suction  passages  be  as  short  and  wide 
as  possible  (to  avoid  wire  drawing  of  the  oil),  and  that  the 
plungers  operate  with  small  pump  chamber  clearance. 

Types  of  Drive. — The  principal  methods  of  driving  mechanical 
lubricators  are: 

Direct  Lever  Drive 

Direct  Rotary  Drive 

Worm  Gear  Drive 

Spur  Gear  Drive 

Ratchet  Drive  and  Ball  or  Roller  Clutch  Drive. 

Lever  Drive  (Fig.  14). — The  plunger  is  operated  by  a  rocker, 
which  gets  its  motion  from  some  part  of  the  engine,  as  for 
example,  the  half  time  shaft  on  a  gas  engine,  Fig.  179,  page  441. 
In  this  way  the  movement  of  the  plunger  can  be  made  to  syn- 
chronize with  the  piston  movement,  and  the  oil  injected  at  a 
definite  moment  in  the  cycle. 

In  large,  slow  speed,  long  stroke  steam  pumping  engines,  the 
oil  can  in  this  way  be  forced  into  the  steam  just  at  the  moment 
when  it  is  required.  It  must  be  noted,  however,  that  such  timed 
injection  of  the  oil  can  take  place  only  in  lubricators  which  pump 
oil  alone,  and  not  oil  and  air,  as  most  lubricators  do  in  which  oil 
drops  through  a  sight  feed  into  the  delivery  pump.  If  air  gets 
pumped  into  the  oil  pipes,  it  has  a  cushioning  effect  and  oil  is 
discharged  only  when  the  back  pressure  is  at  its  minimum. 

Rotary  Drive. — The  lubricator  shaft  has  a  driving  pulley  out- 
side the  container;  the  shaft  revolves  and  may  by  means  of  a 
cam  actuate  the  plunger.  Obviously,  this  form  of  drive  can 


94 


PRACTICE  OF  LUBRICATION 


in  this  way  be  adapted  to  time  the  injection  of  oil  from  the 

various  plungers,  by  suitably  spacing  the  cams  on  the  lubricator 

shaft. 

In  most  lubricators  the  cams 
do  not  actuate  the  plungers 
direct,  as  in  Fig.  13,  but  by  some 
intermediary  mechanism,  which 
in  the  majority  of  cases  is  rather 
unmechanical.  The  most 
common  form  is  that  of  a  cam 
revolving  eccentrically  between 
two  jaws  or  inside  a  slot,  as  in- 
dicated in  Fig.  15,  but  a  cylin- 
drical surface  does  not  wear  well 

^fY")  fTTTT) together  with  a  flat  surface;  the 

FIG.  i4.-Lever  drive.  result  is  therefore  more  or  less 

rapid  wear;  such  motions  fairly 

soon  develop  considerable  backlash,  which  enhances  the  wear. 

Fig.    13   shows   one   method   of   preventing   wear   with  a  cam 


10  000 


' 

\^^^s^/^/ 

: 

££>-. 

FIG.   15. — Cam  motions. 


drive;  the  cam  has  a  loose  roller,  which,  when  pressed  against 
the  plunger  head  by  the  cam,  remains  stationary  during  the  de- 


LUBRICATING  APPLIANCES 


95 


livery  stroke;  the  cam  revolves  inside  the  roller,  and  it  being 
well  lubricated  there  is  no  wear  whatever. 

Worm  gear  and  spur  gear  drives  are  used  for  operating  lubri- 
cators on  high  speed  engines  or  machinery,  so  that  the  pump 
plungers  may  be  made  to  operate  at  a  comfortable  speed  and  with 
fairly  long  strokes. 

Ratchet  drive  and  ball  or  roller  clutch  drive  is  used  when  the 
motion  is  taken  from  some  reciprocating  part  of  the  engine,  as 
for  example,  one  of  the  valve  rods  on  a  steam  engine  (see  Fig.  16). 
Ratchet  drive  is  usually  preferable  to  clutch  drives,  except  at 


FIG.  16. — Ratchet  drive  arrangement. 


low  speeds,  when  there  may  not  be  much  to  choose  between 
them.  At  high  speeds,  the  balls  and  rollers  in  clutches  wear  out 
the  casings,  and  slipping  commences  with  the  too  frequent  result 
that  the  lubricator  stops  working. 

High  speed  ratchet  drives  must  be  carefully  designed;  the 
ratchet  wheel  should  be  made  of  case-hardened  tool  steel  and 
screwed  on  to  the  shaft  in  such  a  manner  that  the  motion  tends 
to  keep  it  in  place.  The  driving  as  well  as  the  backlash  pawls 
should  be  made  very  light,  preferably  of  thin  folded  steel  plate, 
which  presses  only  lightly  against  the  teeth  in  the  ratchet  wheel; 
heavy  pawls,  due  to  inertia  forces,  do  not  act  promptly,  unless 


96  PRACTICE  OF  LUBRICATION 

backed  by  powerful  springs,  in  which  case  rapid  wear  takes  place. 
The  ratchet  should  be  rather  small  and  should  not  move  more 
than  1wo  or  three  teeth  per  stroke;  otherwise  the  driving  pawl 
will  strike  the  teeth  too  hard.  Occasionally,  a  ratchet  wheel 
will  jump  forward  several  teeth,  due  to  lack  of  resistance;  this 
chiefly  occurs  when  the  lubricator  has  only  one  or  two  plungers 
to  operate,  and  can  be  overcome  by  tightening  the  gland  packing 
on  the  lubricator  shaft,  where  it  passes  through  the  container,  or 
by  fitting  some  sort  of  brake  on  the  shaft. 

Lubricators  for  exposed  conditions,  as  for  example,  loco  lubri- 
cators, should  have  the  ratchet  wheel  enclosed  in  an-  oil  tight 
casing  filled  with  oil,  or  the  ratchet  should  be  inside  the  container. 

Feed  Adjustment. — With  ratchet  drive  an  alteration  in  feed 
is  made  by  altering  the  leverage  or  angular  movement  of  the 
actuating  arm,  which  means  a  greater  or  smaller  number  of 
strokes  per  minute.  An  alteration  in  the  amount  of  oil  fed  per 
stroke  can  be  made  by  having  a  by-pass  on  the  delivery  side, 
by  wire  drawing  the  oil  inlet  (suction  passage),  by  altering  the 
stroke  of  the  plunger,  by  keeping  the  suction  valve  or  port  open 
part  of  the  delivery  stroke,  etc.,  etc. 

The  first  two  methods  are  very  unsatisfactory,  particularly 
with  viscous  oils,  as  any  alteration  in  viscosity  means  an  altera- 
tion in  oil  feed.  One  method  of  altering  the  plunger  stroke  is 
shown  in  Fig.  13,  namely,  by  altering  the  position  of  the  two 
adjusting  nuts;  they  may  be  so  adjusted  that  the  plunger  is 
never  touched  by  the  cam  roller  —  no-stroke  position;  or  they 
may  allow  the  cam  roller  to  touch  the  plunger  all  the  time  —  full- 
stroke  position;  any  intermediary  position  can  also  be  secured. 

Keeping  the  suction  ports  or  valves  open  during  part  of  the 
delivery  stroke  has  the  same  effect  as  shortening  the  plunger 
stroke  and  with  a  well-designed  arrangement  is  capable  of  giving 
good  results.  With  the  two  last-mentioned  methods  the  oil 
feed,  assuming  that  the  valve  arrangement  is  satisfactory,  will 
be  maintained  uniform  and  independent  of  the  viscosity  of  the 
oil,  as  long  as  the  speed  is  low  enough  and  the  oil  fluid  enough 
at  the  working  temperature  to  entirely  fill  the  pump  space  on 
the  suction  stroke.  With  steam  cylinder  oils  the  number  of 
long  strokes  per  minute  must  not  exceed  20  to  30  to  get  perfect 
pump  action,  say  above  90  per  cent,  volumetric  efficiency;  with 
medium  viscosity,  internal  combustion  engine  oils,  a  speed  of 
250  to  300  short  strokes  per  minute  may  be  permitted. 

There  are  multiple  feed  lubricators  in  which  one  large  master 
pump  supplies  oil  for  a  number  of  delivery  pumps,  the  feed  to 
each  of  them  being  controlled  by  a  drip-sight  feed;  the  surplus 


LUBRICATING  APPLIANCES  97 

oil  delivered  by  the  large  pump  over  and  above  what  is  taken  by 
the  delivery  pumps  is  by-passed  back  to  the  container  through 
a  loaded  check  valve.  In  this  arrangement  the  oil  feeds  are 
much  influenced  by  alteration  in  viscosity  of  the  oil  (temperature 
changes) ;  also,  an  alteration  in  one  of  the  feeds  affects  the  other 
feeds. 

For  these  reasons  the  author  is  a  strong  advocate  of  separate, 
independent  and  interchangeable  pump  units  for  each  oil  feed, 
as  for  example,  the  pump  unit  in  Fig.  13  which  represents  a 
design  patented  by  A.  Kirkham  and  the  author.  But  this 
principle  of  separate  pump  units  for  each  feed  can,  of  course, 
be  applied  to  any  number  of  designs. 

Heating  Arrangement. — Lubricators  which  are  exposed  to  low 
temperatures  and  have  to  pump  viscous  oils,  as  for  example, 
lubricators  on  locomotives,  steam  traction  engines,  et^.,  must 
be  fitted  with  heating  tubes.  Usually  a  straight  tube  through  the 
container  as  near  the  suction  ports  as  possible,  or  even  a  short 
hollow  tube  screwed  into  the  container,  will  prove  adequate; 
they  must  be  connected  to  the  steam  supply,  say,  ten  minutes 
before  starting,  so  as  to  liquefy  the  oil  sufficiently  to  ensure  good 
pump  action. 

Strainer. — Most  lubricators  have  a  shallow  perforated  strainer 
through  which  viscous  steam  cylinder  oil  passes  so  slowly  that  the 
average  driver  never  troubles  to  use  the  strainer  but  takes  it  out 
when  he  fills  the  lubricator;  even  if  they  are  not  removed,  they 
retain  only  coarse  impurities.  Strainers  are  best  made  of  gauze 
which  has  finer  openings  than  perforated  plate  and  yet  a  con- 
siderably greater  area  of  openings  to  pass  the  oil.  The  strainer 
should  be  deep,  as  shown  in  Fig.  13  and  with  a  solid  bottom  and 
rim,  so  that  any  dirt  or  water  in  the  oil  may  accumulate  here 
while  the  oil  filters  through  the  sides  of  the  strainer. 

Check  Valves. — At  the  extreme  end  of  the  oil  pipes  should  be 
fitted  spring  loaded  non-return  valves  to  prevent  the  oil  pipes 
emptying  themselves;  the  force  of  the  spring  should  be  20-25  Ib. 
per  square  inch,  so  as  to  prevent  a  vacuum  from  opening  the 
valve  and  sucking  oil  out  of  the  pipe  and  lubricator;  this  is  not 
an  unusual  occurrence  with  badly  made  check  valves.  To  ensure 
good  seating  of  the  valve,  the  author  favors  ball  valves  with  the 
spring  soldered  on  to  the  ball;  this  prevents  the  ball  from  rotating 
and  it  forms  a  good  permanent  seating  which  should  preferably 
be  very  narrow. 

Fig.  17  illustrates  one  type  of  check  valve  which  the  author  has 
used  with  great  success.  Fig.  163,  page  399,  shows  a  locomotive 
pattern  check  valve. 


98 


PRACTICE  OF  LUBRICATION 


Desirable  Features  in  Mechanically  Operated  Lubricators. — In 

the  author's  opinion  the  things  to  aim  at  in  the  manufacture  of  a 
first-class  mechanically  operated  lubricator  are  the  following: 

1.  Oil  feeds  independent  of  each  other. 

2.  Oil  feeds  independent  of  viscosity,  oil  level  or  back  pressure. 

3.  Sight  feeds  showing  the  correct  amount  of  oil  actually  passing  out  from 
the  lubricator. 

4.  Oil  feeds  capable  of  quick  adjustment  between  wide  limits. 

5.  Freedom  from  air  lock. 

6.  All  adjustments  outside. 


FIG.  17. — Check  valve. 

7.  All  parts  easily  accessible  for  adjustment,  examination  or  cleaning 

8.  No  joints  under  pressure  except  final  discharge. 

9.  Low  wear  of  parts. 

10.  Efficient  strainer. 

11.  All  pump  units  made  up  of  standard,  interchangeable  parts. 

12.  Adaptability  for  ratchet  drive,  direct  rotary  drive,  worm  gear  drive, 
spur  gear  drive,  or  oscillating  lever  drive. 

13.  Simplicity  and  compactness  of  design. 

14.  Low  cost  of  manufacture. 


CHAPTER  VIII 
BEARINGS 

(Bearings  in  General) 

Bearings  are  used  to  support  the  revolving  or  oscillating  parts 
of  engines  and  machinery,  and  the  problem  of  bearing  lubrication 
is  therefore  the  oldest  of  all  lubricatiug  problems. 

In  the  early  days,  bearings  were  crudely  designed  and  low- 
speed  conditions  prevailed.  The  lubricating  mediae  were  vege- 
table oils  such  as  olive  oil,  rape-seed  and  castor  oil,  and  animal 
fats  and  oils,  such  as  tallow,  lard  oil,  sperm  oil  and  whale  oil. 

The  enormous  development  of  modern  engin.es  and  machinery 
has  brought  into  existence  a  variety  of  bearings  operating  under 
higher  speeds,  higher  pressures  or  higher  temperatures  than  at  any 
time  before.  Lubricating  oils  to  suit  modern  conditions  have  of 
necessity  undergone  a  similar  great  development,  made  possible 
by  the  production  of  mineral  lubricating  oils  manufactured  from 
a  variety  of  petroleum  crudes.  The  subject  of  Bearing  Lubrica- 
tion will  be  divided  into  several  sections  as  follows : 

CONSTRUCTION 
BEARING  MATERIALS 
WORKMANSHIP 
OPERATING  CONDITIONS 
OILING  SYSTEMS 
FRICTIONAL  HEAT 
BEARING  TROUBLES 
LUBRICATION 
SELECTION  OF  OIL 
BEARING  OILS 
SEMI-SOLID  LUBRICANTS 
SOLID  LUBRICANTS. 

CONSTRUCTION 

Bearings  are  made  in  all  sizes  from  very  small  to  very  large  and 
there  are  two  main  types  of  bearings,  as  follows: 

Journal  bearings  Thrust  bearings 

(a)  Solid  bearings.  (a)  Plain  thrust  bearings. 

(6)  Two-part  bearings.  (6)  Ball  and  roller  thrust  bearings. 

(c)  Four-part  bearings. 

(d)  Ball  and  roller  bearings. 

99 


100  PRACTICE  OF  LUBRICATION 

Journal  Bearings,  (a)  Solid  Bearings. — Horizontal  solid  bear- 
ings are  always  small  in  size,  used  as  inexpensive  bearings  for 
loose  pulleys  and  small  shafts  and  in  a  variety  of  machinery  where 
slow  speeds  or  low  bearing  pressures  prevail  or  where  the  lubri- 
cating conditions  are  so  excellent  that  little  or  no  wear  is  antici- 
pated. This  type  of  bearing  is  used  as  gudgeon  or  wrist-pin 
bearing  in  the  great  majority  of  high  speed  steam  engines  and 
internal  combustion  engines. 

When  more  than  slight  wear  is  likely  to  take  place  a  bushing  is 
frequently  provided  so  that  when  the  bushing  is  worn  it  can  be 
replaced. 

Vertical  solid  bearings  are  used  as  neck  bearings  and  footstep 
bearings  for  high  speed  spindles  in  textile  mills,  also  as  footsteps 
for  vertical  shafts. 

(6)  Two-part  Bearings. — The  majority  of  bearings  are  of  this 
type.  For  shafting  bearings  the  two  bearing  halves  are  usually 
of  cast-iron  and  the  bearing  comparatively  long.  They  may  be 
hand  oiled,  drop-feed  oiled,  or  may  be  arranged  for  ring  oiling. 

In  larger  journals  bearing  brasses  are  fixed  in  the  top  and 
bottom  part  of  the  bearing  and  between  the  top  and  bottom 
brasses  are  placed  "  liners  "  which  are  thin  strips  of  metal.  When 
the  bearing  wears,  one  or  more  of  these  strips  may  be  removed, 
so  as  to  bring  the  two  bearing  brasses  closer  together  around  the 
shaft.  Two-part  bearings  are  often  lined  with  anti-friction 
metal. 

Wh  3n  the  pressure  is  always  taken  by  one  of  the  brasses,  say  the 
lower  one,  as  in  many  bearings,  the  top  half  of  the  bearing  need 
not  bo  very  strong  nor  does  the  top  brass  need  to  fit  the  journal 
closely;  in  many  cases  the  top  half  then  simply  acts  as  a  dust 
cover  and  to  hold  the  lubricator.  Railway  axle-boxes,  for  ex- 
ample, have  only  a  top  brass,  the  pressure  being  directed  up- 
ward, and  belo\\  the  journal  is  a  cellar,  holding  a  pad  oiler  or 
waste  packing  for  the  purpose  of  lubricating  the  journal. 

A  two-part  bearing  is  not  suitable  where  the  pressure  from  the 
journal  is  directed  against  the  joint  of  the  two  bearing  halves; 
large  bearings  operating  under  such  conditions  are  therefore 
frequently  designed  as  four-part  bearings. 

(c)  Four-part  Bearings. — These  bearings  are  used  principally 
as  main  bearings  in  large  horizontal  steam  engines  and  gas  engines. 
The  bearing  surface  is  built  up  of  four  parts,  i.e.,  a  top  and  bottom 
brass  and  two  side  brasses. 

(d)  Ball  and  roller  bearings  are  described  in  a  special  chapter. 
Thrust  bearings  are  designed  to  take  up  pressure  in  the  direc- 
tion of  the  shaft,  as  for  instance,  the  propeller  thrust  in  the  case 


BEARIN&d 


101 


of  marine  steam  engines  and  turbines,  etc.  A  special  chapter  is 
devoted  to  the  description  of  plain  thrust  bearings,  and  ball  and 
roller  thrust  bearings  are  described  under  ball  and  roller  bearings. 

BEARING  MATERIALS 

With  perfect  oil  film  lubrication  the  nature  of  the  rubbing 
surfaces  does  not  influence  lubrication,  but  most  bearings  are 
imperfectly  lubricated;  they  wear  more  or  less  and  the  various 
bearing  metals  behave  differently. 

Bearings  are  chiefly  metals,  but  wood,  rawhide,  fibre,  agate 
and  jewels  are  used  for  special  purposes. 

Bearing  Metals. — The  journal  and  the  bearing  should  prefer- 
ably be  of  dissimilar  materials  to  work  well  together,  and  the 
bearing  surface  is  usually  of  a  softer  material  than  the  journal. 
If  wear  takes  place  it  will  then  be  chiefly  on  the  bearing  surface, 
which  is  cheaper  to  replace  than  the  journal. 

Good  bearing  metals  must  possess  the  following  properties: 

1.  Sufficient  strength  to  sustain  the  load. 

2.  Low  running  temperature,  which  means  high  thermal  conductivity; 
white  metals  containing  a  high  percentage  of  lead  are  inferior  in  this  respect 
to  those  rich  in  tin  and  containing  little  or  no  lead. 

3.  Low  Coefficient  of  Friction. — Hard  bearing  materials,  such  as  the  rigid 
bronzes  (copper  tin  alloys  low  in  lead)  are  best  in  this  respect,  assuming 
that  the  bearing  surfaces  are  carefully  fitted  to  the  journal;  otherwise  white 
metals  give  lower  friction  as  they  yield  slightly  and  distribute  the  load  more 
uniformly. 

4.  Durability. — The  rigid  bronzes,  and  alloys  containing  zinc,  wear  more 
than  those  alloys  which  are  rich  in  lead,  but  the  latter  have  a  higher  coeffi- 
cient of  friction.     According  to  Dr.  Dudley  those  bearing  metals  will  wear 
the  least  which  have  a  fine  granular  structure  and  combine  great  elongation 
with  great  tensile  strength,  the  elongation,  however,  being  the  more  im- 
portant property  of  these  two. 

5.  Low  Journal  Wear. — The  white  metals  excel  over  other  metals. 

6.  Ease  of  Replacement. — Again  here  the  advantage  lies  with  the  white 
metals. 

7.  Resistance  to  Corrosion. — Tin  and  antimony  resist  corrosion  best;  iron, 
copper,  lead  and  zinc  are  more  easily  corroded,  particularly  the  two  latter. 
When  the  oil  is  likely  to  contain  a  large  amount  of  free  fatty  acid,  the  white 
metal  should  preferably  contain  no  lead  and  little  or  no  zinc. 

The  following  combinations  of  bearing  metals  represent  current  practice: 

Hardened  Crucible  Steel  on  Steel  or  Bronze. — For  high  pressure  and  low  or 
moderate  speed,  as  for  example,  hard  steel  toggles  working  against  mild 
steel  seats  in  stone  breakers,  presses,  etc. 

Mild  Steel  on  Bronze. — For  moderate  pressures  and  low  or  moderate 
speeds,  as  exist  in  many  important  bearings. 

Mild  Steel  on  White  Metal. — For  low  or  moderate  pressures  and  moderate 
or  highfspeeds.  This  is  the  combination  used  'n  the  great  majority  of 
machinery  bearings. 


102  1'RACTICE  OF  LUBRICATION 

Mild  Steel  on  Cast  Iron. — For  low  or  moderate  pressures  and  low  speeds, 
as  in  textile  machinery  and  the  like;  also  used  for  small  or  medium  size 
shafting  bearings;  the  bearings  are  long  and  the  pressures  low;  with  higher 
bearing  pressures,  the  cast  iron  must  be  lined  with  white  metal. 

Cast  Iron  on  Cast  Iron. — For  low  pressure,  chiefly  used  for  piston  rings, 
cylinders,  crossheads  and  crosshead  guides  in  steam  engines  and  internal 
combustion  engines. 

Hard  Steel,  Bronze  or  Brass. — With  all  hard  bearing  metals  it 
is  important  that  the  bearing  surfaces  be  well  scraped  together 
with  the  journal  and  that  the  bearings  be  carefully  erected,  so 
that  the  pressures  will  be  evenly  distributed  over  the  entire 
bearing  surfaces;  otherwise,  certain  parts  of  the  bearings  will 
be  excessively  loaded  and  cause  heating. 

White  metals  (anti-friction  metals)  are  combinations  of  hard 
metal,  such  as  antimony,  embedded  in  a  soft  plastic  ground  mass, 
such  as  lead. 

When  lined  with  suitable  anti-friction  metal,  which  has  more 
or  less  resilience,  the  journal  easily  beds  itself  down  and  distributes 
the  pressure  uniformly  over  the  entire  bearing  surface. 

In  high  speed  steam  and  internal  combustion  engines,  where 
three,  four  or  five  bearings  support  the  crank  shaft,  the  bearings 
are  nearly  always  lined  with  white  metal,  with  a  view  to  distribut- 
ing the  load  equally  over  all  the  bearings. 

If  bronze  is  used  and  if,  say,  one  bearing  is  slightly  out  of  line, 
the  bronze,  not  yielding,  will  create  excessive  bearing  pressure  in 
that  particular  bearing  and  cause  heating. 

It  is  the  hard  grains  in  a  white  metal  surface  which  sustain 
the  load;  if  the  load  is  excessive  at  any  point,  the  plastic  body  of 
the  metal  will  yield  until  the  load  is  evenly  distributed  over  a 
great  many  hard  grains;  this  will  assist  the  lubricating  oil  in 
maintaining  a  good  film  everywhere  and  means  increased  safety 
in  operation.  If  there  are  only  a  few  hard  grains  in  a  white 
metal,  it  will  be  soft  and  will  stand  only  low  bearing  pressures; 
if  there  are  too  many  hard  grains,  the  points  of  the  hard  crystals 
will  engage  one  another  and  form  a  solid  network  throughout 
the  body  of  the  metal,  which  will  then  be  found  to  be  brittle. 
Tri-metal  alloys  appear  to  give  better  service  than  those  white 
metals  which  are  composed  of  only  two  metals. 

Cast  iron  is  porous  and  granular  in  structure;  close  grained 
cast  iron  is  best  and  can  be  obtained  harder  or  softer  as  required. 
It  is  capable  of  attaining  a  very  smooth,  hard  and  glazed  surface, 
but  if  this  surface  is  cut,  it  takes  considerable  time  to  reproduce 
the  hard  glossy  "skin"  so  very  desirable  from  a  lubrication  point 
of  view. 


BEARINGS  103 

Cast  iron  when  not  exposed  to  undue  pressure  and  well  lubri- 
cated is  a  very  satisfactory  be.aring  metal. 

The  use  of  graphite  in  connection  with  cast  iron  is  capable  of 
giving  excellent  results,  as  mentioned  under  "solid  lubricants." 

Wood,  Rawhide  and  Fibre. — Hard  and  dense  wood  is  used  to 
some  extent  for  spur  and  bevel  gearing  in  windmills,  watermills, 
etc.  For  certain  bearings,  such  as  footsteps  for  water  turbines 
and  stern  tube  bearings,  lignum  vitse  is  favored,  as  it  will  stand 
great  pressure,  is  of  a  greasy  nature,  not  easily  abraded,  and 
works  well  with  water. 

Rawhide  and  fibre,  also  compressed  paper,  are  sometimes  used 
for  pinion  wheels  and  give  silent  running. 

Agate  and  Jewels. — In  watches  and  light  machinery,  which 
cannot  be  regularly  lubricated,  agate  and  various  jewels  are 
used  as  bearings  for  hard  steel  pins. 

WORKMANSHIP 

Workmanship  may  be  defined  as  the  attention  which  has  been 
given  to: 

1.  the  finish  of  the  bearing  surfaces; 

2.  the  bearing  clearance; 

3.  the  alignment  of  the  erected  bearing. 

Finish  of  Bearing  Surfaces. — The  rubbing  surfaces  are  never 
exactly  true  and  smooth.  If  a  new  shaft  is  put  into  new  bearings 
without  oil,  it  will,  when  revolving,  touch  the  bearing  surfaces 
only  at  certain  points,  distributed  more  or  less  evenly  over  the 
surface.  It  is  for  this  reason  that  bearings  are  "scraped  to- 
gether." It  is  an  advantage  to  have  the  surface  of  the  shaft  made 
as  smooth  as  possible  and  the  high  points  in  the  bearing  surfaces 
are  scraped  down  until  finally  the  shaft  bears  uniformly  on  the 
whole  of  the  bearing  area. 

Bearing  Clearance. — The  diameter  of  the  shaft  is  slightly 
smaller  than  the  inside  diameter  of  the  bearing.  The  difference 
between  the  two  diameters — the  bearing  clearance — should  be 
about  Kooo  of  an  inch  per  inch  diameter  of  the  shaft,  rather 
more  than  this  for  small  bearings  and  rather  less  than  this  for 
large  bearings. 

When  the  bearing  surfaces  are  well  lubricated  and  particularly 
when  they  are  supplied  with  a  continuous  stream  of  oil,  which 
carries  away  the  frictional  heat,  the  bearing  clearances^,can  be 
made  smaller,  and  more  efficient  lubrication  can  be  obtained 
than  where  bearings  are  semi-lubricated  and  the  journals  there- 
fore are  more  likely  to  heat  and  expand. 


104  PRACTICE  OF  LUBRICATION 

Alignment. — When  machinery  and  shafting  are  erected,  it  is 
very  important  that  the  various  bearings  be  truly  and  accurately 
fitted.  If,  for  instance,  a  length  of  shafting  is  supported  by  a 
number  of  bearings,  and  some  bearings  are  placed  too  high  and 
others  too  low,  this  will  set  up  stresses  in  the  shafts  and  in  the 
bearings,  creating  difficult  lubricating  conditions. 

OPERATING  CONDITIONS 

Size  of  bearing  (diameter) 
Speed  of  shaft  (surface  speed  per  minute) 
Bearing  pressure  (pounds  per  square  inch) 
Bearing  temperature  (degrees  Fahrenheit) 
Mechanical  conditions  (good  or  bad). 

Size  of  Bearing. — The  surface  of  the  shaft  or  journal  is  never 
perfectly  smooth  nor  round,  but  will  possess  a  roughness  which, 
if  not  visible  to  the  naked  eye,  can  be  seen  through  a  magnifying 
glass.  The  imperfection  in  manufacture  will  have  a  tendency 
to  produce  metallic  contact  between  the  rubbing  surfaces.  This 
tendency  is  greater,  the  larger  the  bearing,  and  experience  has 
proved  that  other  things  being  equal,  the  larger  the  bearing,  the 
heavier  in  body  must  be  the  oil  to  provide  efficient  lubrication. 

Speed  of  Shaft. — A  revolving  shaft  will  draw  the  oil  into  the 
bearing  due  to  the  oil  adhering  and  clinging  to  the  shaft.  Speak- 
ing generally,  this  action  increases  with  the  speed  of  the  shaft 
and  the  body  of  the  oil.  When  bearings  operate  at  low  speed, 
the  oil  used  must  be  heavy  in  body  and  grease  may  be  preferable 
in  some  cases.  At  higher  speeds,  an  oil  light  in  body  should 
preferably  be  used,  and  for  very  high  speeds,  oils  very  light  in 
body  must  be  used. 

At  extremely  high  speeds,  air  even  has  been  used  as  the  only 
lubricant,  as  in  the  case  of  spindle  bearings  for  traverse  spindle 
grinders  used  in  watch  factories.  The  spindles  are  one-half 
inch  in  diameter.  Both  spindles  and  bearings  are  of  hardened 
steel  and  fitted  together  with  extreme  care;  the  fit  is  so  close  that 
when  they  are  not  running  it  is  difficult  to  slide  the  spindle 
through  the  bearing. 

When  starting  up,  the  spindles  will  give  a  grating  noise  for  a 
few  seconds  but  when  attaining  their  normal  speed  of  about 
12,000  R.P.M.  they  run  quite  smoothly  and  with  so  little  friction 
that  when  the  driving  belt  is  thrown  off,  they  continue  to  run  for 
a  couple  of  minutes  until  the  air  film  breaks  and  the  spindles 
quickly  stop.  The  surfaces  must  be  kept  very  clean  by  rubbing 
with  alcohol  and  tissue  paper.  If  the  bearings  or  spindles  are 
not  perfect,  a  little  kerosene  needs  to  be  used  to  give  smooth 
running. 


BEARINGS  105 

Bearing -Pressure. — Bearing  pressures  range  from  a  few  pounds 
per  square  inch  for  cast  iron  piston  rings  -  rubbing  against  cast 
iron  cylinders,  to  as  much  as  3,000-4,000  Ib.  per  square  inch  for 
hardened  steel  rubbing  against  steel,  as  in  slow  speed  punching 
machines.  The  bearing  pressures  are  chiefly  governed  by  the 
nature  of  the  bearing  materials,  the  character  of  the  load  and  the 
degree  of  lubrication  efficiency  desired. 

For  ordinary  conditions  the  bearing  pressures  permissible  for 
various  metals  are  indicated  in  the  following  table: 

Pressures  in  Ib. 
per  sq.  in. 

Hardened  crucible  steel  on  steel 2,000 

Hardened  crucible  steel  on  bronze 1,200 

Unhardened  crucible  steel  on  bronze 800 

Mild  steel  with  smooth   compact  surface  on 

bronze 500 

Mild  steel  with  ordinary  surface  on  bronze.  .  .  .  400 

Mild  steel  with  ordinary  surface  on  white  metal .  500 

Mild  steel  on  cast  iron 300 

Cast  iron  on  cast  iron  (journal  bearings) 100 

These  figures  may  be  increased  50  per  cent.,  100  per  cent.,  or 
even  more,  if  the  load  is  intermittent;  also  if  the  bearings  are 
well  cooled,  as  in  locomotive  crankpins  and  crossheads. 
•  The  figures  must  be  reduced  if  the  pressure  is  always  in  one 
direction  and  never  relieved ;  also,  if  it  is  important  that  no  wear 
should  occur,  as  in  many  electrical  machines  and  other  high  speed 
engines,  such  as  enclosed  type  steam  engines,  gas  engines,  etc., 
lubricated  by  a  circulation  oiling  system.  If  wear  must  not 
take  place,  it  means  that  the  bearings  must  have  perfect  oil  film 
lubrication  at  all  times;  with  high  surface  speed,  higher  bearing 
pressures  may  be  allowed,  as  indicated  in  the  following  formula 
by  H.  F.  Moore,  giving  the  maximum  load  which  can  be  carried 
before  the  film  breaks: 

p  =  7.47  xVv 
in  which  p  =  pounds  per  square  inch 

v  =  surface  speed  in  feet  per  minute. 

In  order  to  ensure  perfect  film  lubrication,  the  bearing  pressure 
must  be  less  than  that  calculated  by  Moore's  formula;  a  factor 
of  safety  may  be  chosen  ranging  from  two  to  eight  according  to 
how  important  it  is  to  prevent  wear. 

All  other  things  being  equal,  it  is  obvious  that  the  greater  the 
pressure  on  the  bearing  and  the  lower  the  speed,  the  heavier  in 
body  must  the  oil  be  to  sustain  the  pressure  without  being 
squeezed  out  too  rapidly.  If  the  pressure  on  the  bearing  is 
slight,  light  bodied  oil  can  be  used,  and  at  moderate  or  high  speeds 


106  PRACTICE  OF  LUBRICATION 

a  moderate  oil  supply  will  be  sufficient  to  maintain  a  complete 
oil  film.  If  the  pressure  on  the  bearing  is  great,  an  oil  heavy  in 
body  must  be  used  and  if  in  addition  the  speed  is  low,  it  is  very 
difficult,  if  not  impossible,  to  maintain  a  complete  oil  film  and  to 
prevent  metallic  contact  of  the  rubbing  surfaces.  It  is  under 
such  conditions  thai  certain  solid  or  semi-solid  lubricants  may 
prove  more  efficient  than  lubricating  oils. 

Bearing  Temperature. — Where  machinery  is  operating  in  cold 
surroundings,  or  at  very  low  speeds,  bearing  temperatures  may 
be  low  (from  70°F  to  90°F.).  When  bearings  operate  in  very  cold 
surroundings,  light  bodied  oils  and  oils  with  low  cold  tests  should 
be  employed,  so  as  not  to  congeal  and  cause  difficulty  in  feeding. 

The  majority  of  bearings  operate  at  medium  temperatures, 
from  90°F.  to  120°F.  High  speed  bearings  frequently  operate 
at  temperatures  higher  than  120°F.,  but  seldom  above  160°F. 
Bearing  temperatures  above  120°F.  must  be  termed  high  and 
should  ordinarily  never  be  allowed  to  exceed  140°F.  (See  Tur- 
bines.) 

If  the  bearing  temperature  is  higher  than  160°F.  the  conditions 
should  be  carefully  looked  into,  as  such  temperatures  are  dan- 
gerous and  show  either  that  the  mechanical  conditions  are  wrong 
and  should  be  corrected,  or  that  the'  quality  of  the  oil  used  is 
unsuitable,  or  that  an  insufficient  quantity  of  oil  reaches  the 
parts  to  be  lubricated. 

If  bearing  temperatures  are  high,  notwithstanding  that  the 
mechanical  conditions  are  correct,  that  carefully  selected  good 
quality  oil  is  used  and  in  sufficient  quantity,  the  conditions  are 
evidently  so  severe  that  the  heat  developed  in  the  bearing,  cannot 
be  radiated  quickly  enough  from  the  bearing  surface.  In  such 
cases,  a  circulation  oiling  system  should  be  introduced,  in  order  to 
remove  the  frictional  heat  and  reduce  the  bearing  temperature 
sufficiently  for  safe  operation. 

Mechanical  Conditions. — Bearings  in  time  will  usually  wear  or 
get  out  of  alignment;  it  is  important  that  the  bearings  be  kept 
in  good  alignment  and  repair,  by  renewing  bushings,  brasses  or 
anti-friction  linings,  by  adjusting  bearings  for  wear,  etc.,  etc. 

When  trouble  or  irregularity  in  operation  occurs  the  cause 
should  be  traced  and  the  conditions  rectified,  rather  than  that 
the  trouble  should  be  allowed  to  continue  until  it  becomes  serious. 

By  good  mechanical  conditions  is  understood,  bearings  of  good 
design,  journals  and  bearing  surfaces  of  good  material,  well 
finished  and  with  suitable  bearing  clearance;  bearings  in  good 
alignment  and  not  appreciably  worn;  also  that  reasonable  atten- 
tion be  given  to  regular  oiling  of  the  bearings. 


BEARINCJS  107 

By  bad  mechanical  conditions  is  understood  bearings  that  are 
crudely  designed,  or  of  good  design,  but  allowed  to  get  out  of 
order;  bearings  made  of  poor  or  unsuitable  material;  bearing  sur- 
faces rough  or  worn,  bearings  out  of  alignment ;  also  lack  of  atten- 
tion in  keeping  the  oiling  system  in  its  most  efficient  state. 

Speaking  generally,  bad  mechanical  conditions  necessitate  the 
use  of  oils  heavy  in  body;  whereas  under  good  mechanical  condi- 
tions oils  lighter  in  body  can  be  employed,  resulting  in  more 
efficient  lubrication  of  the  bearings. 

OILING  SYSTEMS 

The  various  systems  by  which  oil  is  applied  to  bearings  may 
be  divided  into  seven  main  groups,  as  follows: 


INDIVIDUAL  BEARINGS 


HAND  OILING 
DROP  FEED  OILING 
PAD  OILING 
RING  OILING 
BATH  OILING 

{  SPLASH  OILING 
GROUPS  OF  BEARINGS  <  ~ 

(  CIRCULATION  OILING 

Oiling  Systems  for  Individual  Bearings. — Hand  oiling  is  the 
oldest  system  employed  for  lubricating  bearings;  it  is  the  least 
efficient  and  the  most  wasteful  of  all  oiling  systems.  Hand  oil- 
ing is  employed  for  lubrication  of  low  speed  shafting  and  low 
speed  bearings  in  a  variety  of  machines,  such  as  machine  tools, 
textile  machinery,  printing  machines,  etc.  It  is  largely  employed 
for  oiling  small  parts  of  valve  motions,  valve  spindles,  etc.,  in 
steam  engines,  internal  combustion  engines  and  other  power 
producers.  It  is  also  employed  on  various  types  of  machines 
exposed  to  heavy  vibration  or  rough  usage  where  any  kind  of 
lubricating  appliance  would  be  shaken  off. 

In  the  bearing  is  a  hole,  usually  in  the  top  part.  The  oil  is 
applied  by  an  oil  can  preferably  of  the  press-button  type,  by 
which  it  is  possible  to  deliver  one  drop  or  a  few  drops  of  oil  as 
required,  in  order  not  to  waste  too  much.  The  oil  runs  down  the 
hole,  spreads  over  the  bearing  surfaces  and  gradually  works  its 
way  toward  and  out  through  the  ends  of  the  bearing.  After 
each  oiling,  the  oil  film  in  the  bearing  gradually  becomes  thinner, 
and  finally  the  bearing  runs  practically  without  lubrication  until 
such  time  as  it  is  oiled  afresh. 

The  lubrication  will  gradually  decrease  to  a  state  of  inefficiency, 


108  PRACTICE  OF  LUBRICATION 

dependent  upon  the  body  of  the  oil  in  use,  the  length  of  time  be- 
tween oilings  and  the  operating  conditions. 

In  order  to  prevent  the  entrance  of  dust  or  fluffy  matter,  which 
would  tend  to  choke  up  the  oil  hole  or  would  enter  the  bearing 
and  cause  trouble,  the  entrance  to  the  oil  hole  may  be  fitted  with 
an  oil  hole  protector  (see  Figs.  117,  118, 119,  page  290).  Another 
method  is  to  provide  a  felt  pad  in  the  oil  hole  into  which  the  oil 
is  poured.  This  method  insures  more  uniform  feeding  of  the  oil. 

In  many  cases  the  oil  is  not  applied  through  an  oil  hole,  but, 
simply  to  the  end  of  the  bearing,  as  for  example  with  textile 
machinery. 

Drop  Feed  Oiling. — The  drop  feed  oiling  system  includes  all 
appliances  by  which  a  moderate  and  more  or  less  regular  supply 
of  oil  is  fed  to  the  bearing. 

There  are  four  types  of  such  appliances,  namely: 

Syphon  Oiler  Sight  Feed  Drop  Oiler 

Bottle  Oiler  Mechanical  Lubricator. 

Syphon  Oiler. — When  in  the  early  days  of  engineering  hand 
oiling  proved  inadequate  for  lubricating  heavy-duty  bearings, 
the  syphon  oiler  was  the  first  improvement  introduced.  It  (Fig. 
18)  consists  of  a  container  (1)  in  which  oil  is  filled  to  a  certain 
level;  the  syphon  oil  tube  (2)  projects  above  the  oil  level;  the 
syphon  wick  is  introduced  into  the  oil  tube,  its  lower  end  being 
at  a  lower  level  than  the  end  immersed  in  the  oil.  The  oil  level 
should  not  be  allowed  to  be  higher  than  the  top  of  the  oil  tube, 
as  the  surplus  oil  will  then  be  wasted  through  the  tube. 

With  syphon  oilers  the  oil  feed  varies  with  the  oil  level  in  the 
container;  also  with  the  temperature  of  the  oil,  as  cold  and  thick 
oil  will  feed  more  slowly  than  warm  and  thin  oil. 

The  syphon  wick  consists  usually  of  one  or  several  strands  of 
woollen  yarn,  preferably  of  loose  texture,  which  feed  more  freely 
than  yarns  of  tight  twist  and  close  texture.  The  higher  the  oil 
level  in  the  container,  or  the  thinner  the  oil,  or  the  deeper  the 
syphon  is  introduced  into  the  oil  tube,  or  the  greater  the  number 
of  strands  in  the  syphon,  the  greater  will  be  the  oil  feed.  When 
so  many  strands  are  used  that  they  choke  the  oil  tube,  a  point  is 
reached  where  the  addition  of  more  strands  will  reduce  the  oil 
feed  because  of  the  greater  resistance  in  passing  through  the  tight 
syphon;  choke  trimmings  used  in  locomotives  (Fig.  106,  page  274) 
are  of  this  type. 

The  container  should  always  be  fitted  with  a  lid,  so  as  to  pre- 
vent the  entrance  of  dust,  dirt  and  water  into  the  oil.  Syphons 
in  time  get  choked  with  impurities  and  become  inoperative; 
they  should  be  renewed  at  suitable  intervals. 


BEARINGS 


109 


Syphon  oilers  are  rather  wasteful  but  very  reliable  where  a 
moderate  oil  feed  is  required;  they  are  not  suitable  for  very  small 
feeds.  Where  machines  or  engines  are  running  intermittently,  the 
syphons  should  be  lifted  out  of  the  oil  tube  and  left  in  the  oil 


FIG.   18. — Syphon  oiler. 

container  every  time  the  machinery  stops;  otherwise,  they  keep 
on  feeding  and  oil  is  wasted;  oil  should  be  added  to  the  container 
at  frequent  intervals  so  as  to  keep  the  oil  level  as  constant  as 
possible. 

Syphon  oilers  are  employed  for  lubrication 
of  locomotives,  marine  steam  engines,  main 
bearings  of  old-type  stationary  steam  engines, 
and  other  prime  movers,  as  well  as  for  the 
lubrication  of  medium  size  bearings  of  shaft- 
ing and  in  a  variety  of  machines  of  all  kinds. 

The  oil  container  may  have  several  syphon 
tubes,  each  tube  being  served  by  a  separate 
syphon;  such  multiple  feed  syphon  boxes  are 
occasionally  fitted  with  sight  feed  glasses 
below  the  container,  so  that  the  oil  feed  from 
each  syphon  tube  is  visible. 

The  bottle  oiler  (Fig.  19)  has  been  specially 
developed  for  the  lubrication  of  light  and  FlG- 
medium-size  shafting  bearings  operating 
at  low  to  moderately  high  speed  and  under  conditions  which 
make  a  small  constant  feed  desirable.  The  glass  bottle  (1)  has  a 
stopper  (2)  fitted  with  a  brass  tube  (4).  A  copper  or  steel  needle 
(3)  fits  loosely  inside  the  brass  tube,  its  lower  end  resting  on  the 
shaft  in  the  bearing. 

The  shaft,  when  revolving,  gives  the  needle  a  very  slight  up- 


— 3 


19. — Glass 
oiler. 


bottle 


110 


PRACTICE  OF  LUBRICATION 


and-down  motion,  which  has  the  effect  of  drawing  a  sparing  supply 
of  oil  from  the  glass  bottle,  the  oil  creeping  down  over  the  surface 
of  the  needle  and  finally  reaching  the  bearing  surface. 

The  bottle  oiler  is  automatic  in  action,  starting  and  stopping 
with  the  motion  of  the  shaft.  If  the  bearing  gets  warm,  the 
needle  heats  up;  the  oil  surrounding  the  needle  becomes  thinner 
and  more  oil  will  be  fed.  If  the  bearing  vibrates/  the  greater 
movements  of  the  needle  will  result  in  more  oil  being  fed.  If  it 
be  found  that  the  amount  of  oil  supplied  through  the  bottle  oiler 
is  insufficient,  the  oil  feed  can  be  increased  by  using  a  thinner 
needle  or  by  filing  a  flat  on  the  side  of  the  needle. 


1.  Glass  Body 

2.  Oil  Level 

3.  Adjusting  Collar 

4.  Shut-off  Handle 

5.  Top  of  Adjusting  Spindle 

6.  Sight  Feed 

7.  Foot  Valve 

(only  used  when  feeding 
against  intermittent  pres- 
sure) 

FIG.  20. — Sight  feed  drop  oiler. 

The  stopper  should  preferably  have  a  brass  tube,  as  shown,  in 
which  the  needle  has  a  loose  sliding  fit;  without  this  tube  the 
opening  in  the  stopper  varies  considerably  and  in  time  causes  the 
oil  feed  to  stop  on  account  of  the  swelling  of  the  stopper. 

Bottle  oilers  cannot  be  used  on  machinery  exposed  to  rough 
usage,  as  being  of  glass  they  are  easily  broken. 

The  sight-feed  drop  oiler  (Fig.  20)  has  largely  replaced  the 
syphon  oiler.  The  sight-feed  drop  oiler  can  be  adjusted  to  feed 
one  drop  of  oil  per  minute  or  more.  It  consists  of  a  container, 
usually  having  a  glass  body  so  that  the  level  of  the  oil  can  be 
observed.  The  adjusting  needle  or  valve  spindle  (5)  is  guided 
into  a  conical  hole  in  the  bottom  of  the  oiler.  By  turning  the 
milled  collar  (3)  the  needle  can  be  raised  or  lowered  so  as  to  give 
a  greater  or  smaller  feed.  If  the  handle  (4)  of  the  top  of  the 


BEARINGS 


111 


adjusting  needle  (5)  is  turned  to  its  horizontal  position,  the  needle 
drops  by  spring  tension  and  shuts  off  the  oil  supply;  when  it  is 
again  raised,  the  feed  will  be  the  same  as  previously  adjusted. 

Sight-feed  drop  oilers  have  the  same  disadvantages  as  the 
syphon  oiler  as  regards  variation  in  oil  feed,  due  to  higher  or 
lower  oil  level  or  due  to  the  oil  being  cold  and  thick  or  warm  and 
thin;  in  addition,  when  adjusted  to  feed  a  very  small  amount  of 
oil,  grit  and  dirt  may  easily  choke  the  oil  outlet  from  the  oiler, 
so  that  the  feed  stops  altogether.  The  sight-feed  drop  oiler 
has  the  advantage  over  the  syphon  oiler  in  that  the  feed  can  be 
quickly  adjusted,  quickly  started  and  stopped  and  the  oil  level 
as  well  as  the  oil  feed  is  clearly  visible. 

Sight-feed  drop  oilers  may  be  arranged  to  have  more  than  one 
feed.  An  oil  container  may  for  example  have  six  oil  outlets, 
controlled  by  six  different  needle  valves, 
the  oil  dropping  through  sight  feeds  into 
oil  tubes  which  guide  the  oil  to  the  dif- 
ferent bearings. 

Sight-feed  drop  oilers  are  extensively 
used  on  modern  steam  engines  and  power    r 
producers  of  all  kinds.  j 

When  feeding  oil  to  the  crank  pins  of    ( 
steam  engines,  gas  engines  arid  other  prime 
movers,  the  so-called  crank  pin  banjo  oiler 
is  often  employed  (see  Fig.  179,  page  441). 

The  Nugent  crank  pin  oiler,  much  used 
in  the  United  States,  is  shown  in  Fig.  21. 


The  sight-feed  drop  oiler  is  held  in  a  verti-  FIG.    21—  Nugent    crank 
cal  position  by  the  weighted  pendulum  (1) 

to  which  it  is  attached.     The  part  (2)  revolves  centrally,  receives 
the  oil  through  the  tube  (3)  and  guides  it  to  the  crank  pin. 

Mechanically  operated  lubricators,  either  single  feed  or  multi- 
ple feed,  are  occasionally  employed  for  feeding  oil  to  important 
bearings.  The  advantage  is  that,  being  operated  from  some 
moving  part  of  the  engine,  the  mechanically  operated  lubricator 
starts  and  stops  with  the  engine  and  feeds  the  oil  more  uniformly 
and  regularly,  therefore  with  less  waste,  than  when  sight-feed  drop 
oilers  or  syphon  oilers  are  used;  also  a  much  more  viscous  oil  can 
be  fed,  if  required.  The  various  feed  pipes  are  preferably  fitted 
with  check  valves  at  their  extreme  ends  in  order  to  ensure  that 
the  pipes  are  always  filled  with  oil,  so  that  as  soon  as  the  engine 
starts,  and  therefore  the  lubricator,  the  oil  will  immediately  be 
delivered  from  the  ends  of  the  oil  pipes. 

Sight-feed  arrangements  are  either  fitted  in  the  lubricator 


112  PRACTICE  OF  LUBRICATION 

itself,  one  sight  feed  for  each  oil  feed,  or  they  may  be  fitted  at  the 
extreme  ends  of  the  oil  pipes,  the  oil  dropping  from  the  check 
valves  through  sight  feeds  into  the  bearings. 

Pad  Oiling. — Lubrication  by  pad  oilers  or  oil-soaked  waste  is 
chiefly  used  in  railway  practice  and  described  under  railway 
rolling  stock. 

Ring  Oiling. — This  method  is  very  efficient  and  is  described  in 
a  special  chapter. 

Bath  Oiling. — This  system  is  employed  only  for  vertical  bear- 
ings, such  as  ball  bearings,  high-speed  bath  spindles  employed 
in  textile  mills,  or  the  footsteps  of  vertical,  heavy  shafts,  some- 
times found  in  textile  mills,  flour  mills,  vertical  water  turbines, 
vertical  hydro-extractors,  gyratory  crushers,  etc.  (See  under 
respective  headings.) 

Oiling  Systems  for  Groups  of  Bearings. — Splash  oiling  is  em- 
ployed for  lubricating  a  number  of  bearings  enclosed  in  an  oil- 
tight  casing,  this  system  being  frequently  employed  for  lubricating 
enclosed  vertical  or  horizontal  steam  engines,  air  compressors, 
gas  engines,  kerosene  engines,  gasolene  engines,  and  motor  cycles. 

The  enclosed  crank  chamber  is  filled  with  oil  to  a  certain  level; 
means  should  be  provided  to  maintain  this  level  as  constant  as 
possible.  Dippers  fixed  to  the  crank  pin  bearings  (big  ends)  dip 
into  the  oil  and  produce  inside  the  crank  chamber  a  spray  of 
tiny  drops  of  oil  which  reach  and  lubricate  the  main  bearings, 
crank  pins,  gudgeon  or  wrist  pins,  cams,  and  various  other  bear- 
ings or  parts.  The  bearings  have  oil  holes  or  oil  troughs  which 
catch  the  oil  from  the  spray  and  guide  it  into  the  bearing  surf  aces. 

In  some  small  steam  engines,'  in  motor  cycle  engines,  and 
certain  types  of  automobile  engines,  the  crank  disc  or  the  fly- 
wheel revolving  inside  the  crank  chamber  may  be  arranged  so 
that  it  dips  into  the  oil,  and  as  the  oil  adheres  to  the  revolving 
rim  an  oil  spray  will  be  produced.  Oil  wells  or  pockets  may  be 
cast  on  the  inside  of  the  casing,  collecting  the  oil  and  assisting  it 
through  various  channels,  tubes  or  troughs,  in  reaching  all  parts. 

If  the  oil  level  is  too  low,  too  little  oil  spray  will  be  formed ;  some 
of  the  parts  will  be  starved,  resulting  in  inefficient  lubrication. 
If  the  oil  level  is  too  high,  too  much  oil  spray  will  be  formed,  which 
always  results  in  waste  of  oil,  the  oil  spray  escaping  from  the  bear- 
ings or  from  the  air  vent  usually  provided  in  the  crank  chamber. 

Excessive  oil  spray  in  the  case  of  automobile  engines  and  motor 
cycles,  and  other  internal  combustion  engines,  is  detrimental, 
producing  excessive  carbonization  on  the  hot  pistons.  In  the 
case  of  vertical  steam  engines,  excessive  oil  spray  means  that 
too  much  oil  passes  the  pistons  and  finds'its  way  through  the 


BEARINGS  113 

engine  with  the  exhaust  steam;  this  means  always  waste,  and 
sometimes  trouble  where  it  is  important  that  the  exhaust  steam 
should  be  as  free  from  oil  as  possible. 

Circulation  Oiling. — There  are  two  main  systems  embodying  the 
circulation  principle,  viz: 

Gravity  Feed  Circulation. 
Force  Feed  Circulation. 

The  Gravity  Feed  Circulation  System  is  a  central  automatic 
oiling  system  for  lubricating  a  number  of  bearings  and  parts,  as 
for  instance,  the  main  bearings,  crank  pins,  crossheads,  cross- 
head  guides,  etc.,  etc.,  comprising  most  of  the  external  moving- 
parts  in  medium  or  large  size  open  type  steam  engines,  gas 
engines,  Diesel  engines,  steam  turbines,  groups  of  large  shafting 
bearings,  etc. 

Oil  is  fed  by  gravity  from  a  top  supply  tank  through  a  dis- 
tributing pipe  and  its  branch  pipes  leading  to  the  various  bear- 
ings. Adjusting  cocks  are  fitted  in  these  branch  pipes  so  as  to 
regulate  the  oil  feeds,  and  sight  feeds  are  frequently  fitted  in  the 
oil  inlet  or  outlet  pipes  to  the  bearings  so  that  the  oil  feeds  are 
clearly  visible.  Sometimes,  as  in  the  case  of  steam  turbines,  the 
sight  feeds  are  fitted  in  the  outlets  from  the  bearings,  showing 
the  amount  of  oil  which  has  passed  through  the  bearings.  Having 
done  its  work,  the  oil  drains  back  from  the  various  parts  through 
return  oil  pipes  to  a  bottom  receiving  tank.  The  oil  pump  driven 
by  the  engine  takes  the  oil  from  the  receiving  tank  and  delivers  it 
either  through  an  oil  cooler  or  direct  into  the  top  supply  tank. 
If  more  oil  is  delivered  to  the  top  tank  than  is  required  for  the 
bearings,  the  surplus  oil  passes  through  an  overflow  back  into 
the  bottom  receiving  tank. 

Drain  pipes  are  fitted  to  the  top  tank  and  bottom  tank  to 
enable  the  operator  to  drain  out  water,  sludge  or  impurities 
when  required;  also  the  whole  or  part  of  the  contents  of  the 
tanks  may  be  withdrawn  for  treatment  in  a  separation  and  fil- 
tration plant. 

It  is  always  difficult  to  avoid  some  loss  of  oil.  Oil  is  lost  in 
the  form  of  oil  spray,  particularly  when  the  speeds  are  high, 
and  is  wasted  through  tiny  leaks  difficult  to  avoid  and  often 
difficult  to  locate.  The  loss  of  oil  can  be  reduced  somewhat 
by  reducing  the  amount  of  oil  fed  to  each  bearing,  but  this  is 
doubtful  economy,  if  the  lubrication  becomes  less  efficient; 
sufficient  oil  should  be  fed  so  that  a  good  oil  film  will  be  main- 
tained, and  friction  and  wear  reduced  to  a  minimum. 

A  heavy  viscosity  oil  will  cause  less  loss  by  leakage  or  oil 


114  PRACTICE  OF  LUBRICATION 

spray  than  a  low  viscosity  oil;  but  here  again,  the  bearing  fric- 
tion -is  usually  increased,  so  that  very  viscous  oils  should  be 
introduced  from  an  oil  loss  point  of  view  only  if  the  leakage 
losses  are  quite  abnormal.  It  pays  to  provide  good  savealls 
and  splashguards,  not  only  to  save  oil,  but  also  to  save  the 
foundations.  Oil-soaked  parts  of  a  foundation  are  weak  and 
crumbly,  and  a  constant  source  of  danger  for  the  engine. 

The  force  feed  circulation  system  operates  on  lines  exactly 
similar  to  the  gravity  feed  circulation  system,  the  difference  being 
that  the  top  tank  is  omitted  and  the  oil  passes  direct  into  the 
distributing  pipe,  which  should  preferably  be  fitted  with  an  ad- 
justable relief  valve,  a  portion  of  the  oil  being  by-passed  back 
into  the  bottom  tank.  The  oil  is  thus  delivered  under  pressure 
as  direct  as  possible  to  the  various  bearings  and  parts  requiring 
lubrication. 

This  system  is  largely  employed  for  lubricating  all  sizes  of  en- 
closed type  steam  engines,  Diesel  engines,  vertical  kerosene 
engines,  gasolene  engines,  steam  turbines,  etc. 

Daily  Treatment. — In  the  cases  of  both  splash  oiling  and  oil 
circulation  it  is  good  practice  to  remove  two  to  six  gallons  of  oil 
every  day  for  treatment  in  a  heated  separating  tank  to  separate 
out  water,  sludge  and  impurities,  and  afterward  to  pass  the  oil 
through  a  good  filter;  the  purified  oil,  mixed  with  a  little  fresh 
oil  should  be  returned  to  the  system  at  the  same  time  that  a  cor- 
responding quantity  of  oil  is  removed  from  the  system  for  treat- 
ment. When  the  oil  tank  capacity  in  the  system  is  small,  it  is 
particularly  desirable  to  recommend  this  practice.  In  this  way 
the  vitality  of  the  oil  is  kept  up  to  as  high  a  standard  as  possible 
and  the  life  of  the  oil  is  greatly  increased. 

In  very  large  plants,  the  separation  and  the  filtration  apparatus 
are  preferably  constructed  as  a  part  of  the  circulation  system,  so 
that  either  the  whole  of  the  oil  in  circulation  or  a  certain  percent- 
age of  it  is  constantly  passed  through  the  purifying  apparatus. 

Care  of  Oiling  Systems. — Whatever  oiling  systems  may  be 
employed,  it  is  important  that  the  necessary  attention  be  given 
to  institute  a  regular  routine  for  maintaining  the  oiling  systems 
at  their  highest  efficiency. 

Bearings  that  are  hand  oiled  should  be  oiled  at  sufficiently 
frequent  intervals  to  ensure  the  presence  of  an  oil  film  and  pre- 
vent excessive  heating.  The  oil  containers  in  syphon  oilers, 
bottle  oilers,  sight-feed  drop  oilers,  mechanically  operated  lubri- 
cators should  be  filled  at  correct  intervals,  and  a  regular  system 
should  be  employed  for  putting  the  oilers  into  and  out  of  service 
as  may  be  required.  Lubricators  never  should  be  allowed  to 


BEARINGS 


115 


run  empty  or  to  get  choked  with  dirt,  and  they  should  be  cleaned 
occasionally. 

OIL  DISTRIBUTION 

Reaching  the  bearing,  the  oil  is  conducted  to  the  bearing  sur- 
faces through  drilled  holes;  in  order  to  prevent  oil  being  wasted 
between  the  bearing  cap  and  brass  a  tube  should  be  tightly  fitted 
at  this  point.  The  edges  of  the  brasses  at  the  side  where  the 
oil  enters  should  be  chamfered,  so  as  to  facilitate  the  entrance  of 
the  oil  to  the  bearing  surface.  This  is  of  paramount  importance. 

In  bearings  employing  the  ring  oiling,  splash  oiling  and  circu- 
lation oiling  systems,  where  the  bearings  are  copiously  supplied 
with  oil,  oil  grooves  are  nearly  always  detrimental;  there  is 
usually  only  an  oil  distributing  groove,  which  runs  nearly  the 
whole  length  of  the  bearing.  This  oil  distributing  groove  should 
be  on  the  side. of  the  bearing  where  the  direction  of  the  revolu- 
tion of  the  shaft  is  downwards,  and  its  lower  edge  should  be 
chamfered  so  as  to  facilitate 
the  entrance  of  the  oil. 

In  bearings  that  are  hand 
oiled  or  lubricated  by  a  drop 
feed  system,  in  which  only  a 
moderate  supply  of  oil  is  in- 
troduced into  the  bearings, 
and  where  a  perfect  oil  film 
does  not  exist,  it  sometimes 
becomes  desirable  not  only  to 
have  an  oil-distributing 
groove,  but  also  to  have  other  suitably  cut  oil  grooves  to  dis- 
tribute the  oil  to  the  bearing  surface. 

Under  the  influence  of  the  bearing  pressure  the  oil  is  squeezed 
toward  the  edges  of  the  brass;  if  the  surface  speed  is  high,  it  will 
be  only  a  small  portion  which  escapes,  and  the  loss  is  replaced  at 
the  place  where  the  oil  enters  the  bearing.  If  the  surface  speed 
is  low,  the  oil  received  by  a  certain  part  of  the  journal  gets  time 
to  escape  and  leave  the  journal  surface  unlubricated  long  before 
that  particular  point  has  completed  a  revolution  and  can  receive 
more  oil.  It  is  under  these  conditions  that  a  very  viscous  oil  of 
good  body  should  be  used  and  that  oil  grooving  is  desirable.  The 
oil  grooves  should  be  so  cut  as  to  feed  oil  to  several  points  in  the 
bearing  and  so  renew  the  oil  film  at  these  points.  Oil  grooving 
is  frequently  much  overdone.  Cutting  large  oil  grooves  removes 
the  bearing  surface  which  supports  the  shaft;  it  is  only  in  large, 
slow  speed,  heavy  duty  bearings  that  oil  grooving  may  become 
desirable. 


FIG.  22. —  Oil  grooving  a  large  crank  pin 
bearing. 


116  PRACTICE  OF  LUBRICATION 

Fig.  22  illustrates  oil  grooving  in  a  large  crank  pin  bearing. 
The  oil  is  introduced  at  the  top,  and  the  action  of  the  oil  grooves 
is  partly  to  distribute  the  oil  and  partly  to  guide  it  back  toward 
the  middle  of  the  bearing,  in  order  to  prevent  it  from  escaping 
too  freely  over  the  ends  of  the  bearing. 

Oil  grooves  should  always  be  cut  shallow  and  have  rounded 
edges;  they  should  not  come  too  close  to  the  end  of  the  bearing 
brasses;  if  they  are  cut  close  to  the  ends,  oil  runs  away  too  freely, 
is  wasted,  and  the  bearing  will  be  inclined  to  heat. 

FRICTIONAL  HEAT 

The  frictional  heat  developed  in  a  bearing  spreads  into  the 
journal  and  into  the  bearing  itself.  Where  bearings  are  not 
watercooled  or  lubricated  by  a  circulation  oiling  system,  the 
whole  of  the  heat  developed  must  leave  the  bearing  or  journal 
by  radiation  into  the  atmosphere.  Bearings,  therefore,  assume 
a  temperature  higher  than  the  surrounding  room  temperature, 
and  the  higher  the  friction  the  greater  will  be  the  difference 
between  the  temperature  of  any  part  of  the  bearing  and  the 
room  temperature.  The  difference  is  termed  the  frictional  rise 
in  temperature,  or  simply  the  frictionai  temperature,  and  forms  a 
true  guide  as  to  the  quality  of  the  oil  in  service.  Any  reduction 
in  the  frictional  temperature  brought  about  by  introducing 
another  lubricant  will  mean  that  this  lubricant  is  better  in 
quality  or  more  suitable  for  the  conditions. 

The  frictional  temperature  remains  practically  constant  for 
all  room  temperatures;  i.e.,  if  the  bearing  temperature  is  86°F. 
and  the  room  temperature  is  70°F.,  the  frictional  temperature 
is  16°F.  If  the  room  temperature  rises  to  74°F.  it  will  be  found 
that  the  bearing  temperature  will  rise  to  90°F;  the  friction 
developed  is  practically  the  same,  and  the  bearing  temperature 
must  therefore  be  correspondingly  higher,  in  order  to  radiate  the 
same  amount  of  heat  into  the  atmosphere. 

When  bearings  operate  under  conditions  of  high  speed  or 
pressure  the  heat  developed  may  become  so  great  that  it  cannot 
be  radiated  from  the  bearing  surfaces  sufficiently  rapidly.  Under 
such  conditions  it  becomes  desirable  or  necessary  to  introduce  a 
circulation  oiling  system  by  which  the  flow  of  oil  going  through 
the  bearings  not  only  serves  to  lubricate,  but  also  removes  a 
large  portion  of  the  heat  developed,  so  that  this  heat,  carried 
away  with  the  oil,  can  be  radiated  into  the  atmosphere  from  the 
oil  tanks,  oil  pipes,  etc.,  or,  if  necessary,  can  be  removed  by  an 
oil  cooling  arrangement,  as  in  steam  turbines. 


BEARINGS  117 

BEARING  TROUBLES 

Where  trouble  occurs,  it  is  usually  indicated  by  a  tendency  of 
the  bearings  affected  to  heat  up.  It  will  be  instructive  to  analyze 
a  number  of  the  causes  leading  to  heated  bearings. 

When  the  barrels  of  oil  have  been  delivered,  it  is  important 
that  they  be  stored  under  cover;  they  should  not  be  left  in  the 
open,  exposed  to  sun  and  rain,  as,  particularly  if  the  barrels  are 
stood  on  end,  rain  water  will  find  its  way  through  the  staves, 
resulting  in  the  glue  lining  on  the  inside  of  the  barrel  being 
dissolved  and  spread  throughout  the  oil.  When  such  oil  is  used, 
the  presence  of  lining  material  will  cause  excessive  heating  in  the 
bearings. 

When  opening  a  barrel,  the  bung  should  be  loosened  by  striking 
the  staves  with  a  mallet;  if  an  auger  be  used,  fine  chips  of  wood, 
and  dirt  from  the  outside  of  the  barrel,  may  easily  find  their  way 
through  the  opening  into  the  oil.  The  oil  should  therefore  always 
be  poured  through  a  strainer  into  the  oil  cans.  If  this  be  not  done, 
the  small  chips  of  wood  and  other  impurities  may  get  into  the 
bearings  and  cause  trouble. 

When  the  oil  is  given  out  from  the  barrels  direct,  the  overflow 
oil  runs  on  to  the  floor  or  into  savealls,  which  are  not  always  clean, 
and  there  is  the  danger  that  some  of  this  oil,  including  the  dirt 
present  will  be  given  out  for  lubrication. 

It  is  good  practice  to  keep  the  oils  in  cabinets,  preferably  pad- 
locked, so  that  the  oil  is  not  interfered  with  by  unauthorized 
persons;  there  is  then  no  waste  oil. 

Dirty  oil  cans  are  responsible  for  many  hot  bearings,  and  they, 
should  therefore  be  kept  scrupulously  clean;  they  should  be 
closed  at  the  top  or  provided  with  covers,  so  as  to  prevent,  as 
far  as  possible,  the  entrance  of  dirt. 

An  oil  can  should  never  be  used  for  more  than  one  class  of  oil, 
and  in  order  to  prevent  mistakes  the  name  of  the  oil  should  be 
marked  on  the  can. 

Numerous  hot  bearings  have  been  caused  by  the  wrong  oil 
being  used.  If,  say,  a  spindle  oil  is  used  instead  of  an  engine  oil, 
it  will  cause  heating,  because  it  is  too  light  in  body  to  provide 
lubrication.  If  a  very  heavy  oil  is  used  in  place  of  spindle  oil, 
it  will  cause  heating  and  the  fluid  friction  will  be  excessive, 
because  it  is  too  heavy  to  spread  over  the  bearing  surfaces,  owing 
to  the  high  speed  at  which  the  spindles  operate. 

In  some  cases,  oils  like  linseed  oil  or  turpentine  have  been  used 
by  mistake;  in  other  cases,  the  use  of  badly  filtered  oil  or  waste 
oil,  instead  of  fresh  oil,  has  caused  great  trouble. 


118  PRACTICE  OF  LUBRICATION 

When  hand  oiling  is  employed,  bearings,  will  be  inclined  to 
heat  up  if  the  oilings  are  not  sufficiently  frequent. 

When  drop  feed  oiling  is  employed  many  hot  bearings  are 
caused  by  the  lubricator  running  empty  particularly  when  the  oil 
containers  are  of  small  capacity.  Sometimes  bearings  heat  up 
because  the  oil  congeals  in  the  lubricator  or  in  the  feed  pipes  and 
does  not  reach  the  bearings. 

Sometimes  parts  of  the  lubricator,  or  the  oil  feed  pipes  from 
the  lubricator  to  the  bearings  get  choked  up  with  deposits  of 
various  kinds,  which  may  cause  a  reduction  in  the  oil  feed,  re- 
ducing it  to  such  an  extent  that  the  bearing  heats  up. 

Fine  sawdust  in  saw  mills,  or  wood-working  shops,  flour  dust 
in  flour  mills,  lint  in  cotton  mills,  etc.,  have  been  responsible  for 
such  trouble.  In  one  case  the  sight-feed  drop  oilers  were  invaded 
by  thousands  of  tiny  little  flies,  which,  after  a  while,  completely 
choked  the  feed  pipes  from  the  lubricators  to  the  bearings. 

Cotton  waste,  still  largely  used  for  cleaning  down  engines  and 
machinery,  should  not  be  used  for  this  purpose,  as  fine  fluffy 
matter  from  the  waste  gets  into  the  lubricators  and  oil,  causing 
trouble.  Mutton  or  silk  cloths  are  much  to  be  preferred,  as  they 
are  free  from  fluffy  matter  and  can  be  readily  cleaned. 

Oil  may  escape  between  the  bearing  keep  and  the  bearing 
brass,  instead  of  entering  the  bearing.  With  a  liberal  oil  feed, 
the  bearing  will  give  no  trouble,  but  when  even  a  small  reduction 
in  the  oil  feed  is  attempted,  the  bearing  will  heat  up,  as  it  is 
only  the  surplus  oil  that  reaches  the  bearing  itself. 

Very  long  bearings  sometimes  give  trouble  if  they  have  too 
few  entrances  for  the  oil.  For  instance,  a  bearing  more  than  10 
inches  long  and  having  only  one  oil  inlet  by  the  drop  feed  method, 
in  the  centre,  will  always  be  inclined  to  give  trouble. 

Some  bearings  are  difficult  to  lubricate  because  the  pressure  is 
upward,  instead  of  downward,  which  makes  it  difficult  for  the 
oil  to  spread,  unless  it  is  introduced  at  the  bottom  of  the  bearing. 

In  the  case  of  ring  oiling  bearings,  water  of  condensation  from  a 
very  moist  atmosphere  may  enter  and  accumulate  in  the  bottom 
of  the  bearing,  and  will  lift  the  oil  out  of  the  bearing,  until  finally 
the  oil  rings  revolve  in  water  and  heating  occurs.  In  ring  oiling 
bearings,  deposits  formed  by  the  oil  itself  or  by  impurities  entering 
the  bearing  may  cause  the  oil  rings  to  stick,  so  that  the  oil  supply 
fails  and  the  bearing  heats  up. 

Bearings  lubricated  by  the  splash  oiling  system  may  heat,  due 
to  the  oil  level  being  too  low  to  provide  adequate  oil  spray,  or 
due  to  emulsification  of  the  oil,  by  the  presence  of  water  of  con- 
densation and  cylinder  oil  coming  from  leaking  glands. 


HEARINGS  119 

Water,  either  from  the  engine  itself,  such  as  condensed  steam 
from  leaking  piston  rod  glands,  or  leaking  cooling  water,  etc., 
etc.,  may  find  its  way  into  the  bearings  and  displace  the  oil; 
the  bearings  start  heating  as  soon  as  the  oil  film  is  destroyed  by 
the  water. 

Where  the  entrance  of  water  cannot  very  well  be  avoided,  the 
system  of  daily  treatment  of  the  oil  (see  under  "Turbines")  will 
always  bring  about  an  improvement. 

In  circulation  oiling  systems  bearings  may  heat  due  to  deposit 
choking  the  oil  inlet  pipes. 

Deposits  may  be  due  to  unsuitable  or  improperly  manufac- 
tured oil,  or  to  the  mixing  of  water  and  oil,  or  of  two  different 
oils.  If,  for  example,  an  oil  heavily  compounded  with  blown 
vegetable  oils  gets  into  the  mineral  oil  in  circulation,  a  large 
portion  of  the  compound  will  separate  out  in  the  form  of  a  sludge. 

If  mineral  oil  has  been  a  long  time  in  circulation  and  has  be- 
come very  dark  in  color  and  considerably  weakened,  the  addi- 
tion of  a  large  quantity  of  fresh  oil  will  throw  down  a  dark 
colored  deposit. 

Oil  distributing  grooves  or  oil  grooves  in  the  bearings  may  be 
choked  up  for  various  reasons  already  given  and  thus  cause 
trouble,  in  preventing  the  proper  distribution  of  the  oil. 

Speeding  up  of  the  machinery,  in  order  to  increase  production, 
may  cause  heating,  as  obviously  higher  speed  will  produce  higher 
friction  and  may  demand  the  selection  of  a  more  quick-acting  or 
higher  quality  oil  to  give  good  results. 

If  the  load  on  an  engine  is  increased,  it  is  not  unusual  to  find 
that  some  of  the  bearings  are  not  able  to  sustain  the  increased 
strain,  and  therefore  heat. 

Excessive  strains  in  the  bearings  may  also  be  produced  by  the 
settling  of  foundations,  which  throws  the  bearings  out  of 
alignment. 

Excessive  vibration  may  produce  similar  results. 

Light  load  on  a  steam  engine  may  cause  heating  of  the  crank 
pin  bearing,  there  being  an  insufficient  quantity  of  steam  in  the 
cylinder  to  cushion  properly  the  movement  of  the  heavy  piston, 
so  that  the  crank  pin  is  subjected  to  excessive  pressures. 

Eccentric  straps  may  heat  due  to  bad  internal  lubrication,  which 
increases  the  resistance  in  moving  the  steam  or  exhaust  valves. 

Driving  belts  and  ropes  after  a  time  become  slack  and  must  be 
shortened.  If  they  are  shortened  too  much,  they  produce 
excessive  pressure  on  the  bearings  supporting  the  pulleys  over 
which  the  belts  or  ropes  run. 

Excessive  moisture  in  the  atmosphere  causes  cotton  belts  or 
ropes  to  shrink,  whereas  leather  belting  stretches. 


120  PRACTICE  OF  LUBRICATION 

In  textile  mills  where  a  number  of  the  high  speed  spindles  are 
operated  by  cotton  tapes  and  bands,  the  shrinkage  of  the  cotton 
due  to  excessive  moisture  puts  excessive  pressure  on  the  spindle 
bearings  and  causes  heating. 

Increased  temperature  will. thin  the  oil,  so  that  it  may  not  be 
able  to  withstand  the  bearing  pressures;  for  example,  a  new  addi- 
tion to  a  boiler  plant  in  close  proximity  to  the  power  house  in- 
creased the  temperature  of  an  engine  room  so  much  that  all 
bearings  heated  until  an  oil  heavier  in  body  was  introduced. 

Excessive  load  on  an  electric  motor  or  the  electrical  part  being 
out  of  order,  will  cause  high  temperature  in  the  rotor;  the  extra 
heat  thus  conducted  into  the  bearings  may  cause  the  oil  film  to 
break  down,  indicated  by  excessive  heating. 

In  many  classes  of  rough  machinery,  it  is  still  frequent  prac- 
tice to  replace  bearings  without  any  attention  being  given  to 
scraping  them  together  with  the  shafts;  in  fact,  the  bearings  are 
allowed  to  "run  themselves  in,"  developing  considerable  heat 
and  necessitating  a  liberal  feed  of  heavy  bodied  oil  during  the 
first  few  days.  Needless  to  say,  this  is  a  crude  and  undesirable 
practice. 

Whenever  a  bearing  has  been  excessively  hot,  the  bearing 
brasses  warp,  the  cheeks  of  the  brass  closing  against  and  nipping 
the  shaft;  it'  is  necessary  to  file  away  and  chamfer  the  edges  so 
as  to  facilitate  the  entrance  of  the  oil. 

Cracked  bearing  brasses  allow  the  oil  to  leak  away;  the  oil  film 
is  destroyed,  and  even  with  a  liberal  oil  feed  the  bearing  will  be 
sensitive  and  inclined  to  heat. 

Too  soft  white  metal  often  causes  heated  bearings;  as  it  yields 
to  the  pressure  and  slowly  flows  out  of  the  bearing^,  so  that  the 
bearing  surface  constantly  changes  and  never  assumes  a  good 
working  skin. 

Too  hard  bearing  metal  frequently  results  in  heating,  because 
the  bearing  pressures  are  not  uniformly  distributed  over  the 
surfaces. 

Rebabbitting  of  a  bearing  should  be  done  in  one  pouring;  if 
done  in  two  pourings,  the  white  metal  already  in  the  bearing 
will  have  partly  solidified  and  will  not  melt  properly  together 
with  the  white  metal  poured  in  last.  The  result  will  be  that  in 
operation  cracks  will  develop  and  the  white  metal  will  break 
loose.  This  also  occurs  when  the  white  metal  has  been  poured 
too  cold,  as  it  does  not  adhere  closely  to  the  shell. 

After  a  bearing  is  rebabbitted,  the  bearing  edges  should  be 
rounded  off,  and  all  necessary  oil  hoies  and  distributing  grooves 
property  made.  Failure  in  these  respects  will  cause  heating  of 
the  bearing. 


BEARINGS  121 

If  appreciable  wear  takes  place,  the  edges  of  the  oil  grooves 
become  sharp  and  act  as  oil  scrapers  rather  than  oil  distributors. 
The  edges  must  be  kept  well  rounded  and  the  oil  grooves  should 
therefore  occasionally  be  examined,  particularly  if  trouble  has 
occurred. 

When  worn  bearing  brasses  have  been  replaced,  the  bearings 
sometimes  heat  because  the  new  brasses  have  not  been  properly 
fitted  or  scraped  together. 

With  crank  shafts  and  the  like  which  have  recessed  journals 
for  the  main  bearings  provided  with  filleted  corners,  heating 
may  occur  if  the  shaft  has  insufficient  room  to  float  sideways,  as 
the  shaft  will  bear  hard  against  the  fillet;  expansion  of  the  shaft 
may  be  the  cause  of  this  kind  of  heating;  another  cause  is  men- 
tioned on  page  163  for  electric  dynamos. 

If  the  bearing  clearance  is  too  small,  through  too  close  adjust- 
ment, heating  will  occur,  as  there  is  insufficient  room  for  the  oil 
to  produce  a  satisfactory  film,  and  it  becomes  difficult  for  the 
oil  to  spread. 

If  the  adjustment  of  a  bearing  is  too  loose,  the  oil  escapes  from 
the  bearing  too  freely,  and  particularly  in  the  case  of  bearings 
like  crank  pin  bearings,  which  are  subjected  to  intermittent 
heavy  pressures,  the  oil  will  not  be  able  to  give  sufficient  cushion- 
ing effect  to  prevent  metallic  contact;  pounding  or  knocking  of 
the  bearing  takes  place,  resulting  in  heating  and  wear. 

In  starting  up  after  a  stoppage,  say,  over  Sunday,  certain  bear- 
ings may  be  inclined  to  heat,  as  the  power  necessary  to  drive 
the  mill  or  works  is  always  a  good  deal  higher  than  normal. 

When  engines  and  machinery  have  been  shut  down  for  a  longer 
period,  very  special  attention  should  be  given  to  the  lubricators 
and  lubrication  of  all  parts  before  recommencing  operation; 
driving  belts  and  ropes  are  stiff  after  the  long  standstill,  and  it 
must  not  be  expected  that  the  plant  can  be  quickly  run  up  to 
speed  without  trouble. 

Excessive  deflection  of  a  shaft  due  to  various  causes  will  result 
in  overheating  of  the  nearest  supporting  bearings,  as  the  shaft 
will  bear  more  heavily  on  one  side  of  the  bearings,  the  heat 
developing  and  spreading  from  here. 

When  bearings  of  electric  motors  or  generators  wear,  the  slight 
lowering  of  the  rotor  due  to  this  wear  will  cause  the  magnetic  field 
to  exert  a  strong  downward  pull  on  the  rotor,  thus  increasing  the 
tendency  to  wear  and  causing  excessive  heating. 

Where  oils  of  vegetable  or  animal  character,  or  at  least  heavily 
compounded  oils  have  been  used,  and  where  the  new  oil  intro- 
duced is  straight  mineral  or  nearly  so,  the  change  over  should 


122  PRACTICE  OF  LUBRICATION 

take  place  gradually,  as  vegetable  and  animal  oils  produce  a 
sticky,  varnish  or  rubber-like  coating  all  over  the  bearing  surfaces 
and  in  the  oil  pipes.  //  the  change  is  made  quickly,  heating  is 
bound  to  occur  or  even  seizure  of  the  bearing  surfaces,  as  the 
coating  is  loosened  in  lumps  or  flakes,  preventing  proper  oil 
film  formation.  It  takes  time  for  the  bearing  surfaces  to  adapt 
themselves  to  the  new  oil. 

When  introducing  a  new  oil  which  is  appreciably  different  in 
character  from  the  oil  previously  in  use,  it  will  nearly  always  be 
found  that  some  bearings  heat  up.  This  may  be  due  to  a  mineral 
oil  dissolving  deposits  produced  by  a  compounded  oil,  which  on 
being  too  quickly  loosened  cause  trouble,  acting  in  the  same  way 
as  grit  or  dirt. 

The  use  of  a  grease  containing  dirt  (which  is  not  visible  as  in 
oil)  and  coarse  graphite  tends  to  choke  oil  pipes  and  oil  grooves 
and  is  often  responsible  for  heated  bearings. 

It  is  not  unusual  to  find  that  a  number  of  bearings  in  a  mill  are 
using  far  too  heavy  an  oil,  because  a  few  bearings,  operating  under 
bad  mechanical  conditions  have  demanded  its  use  to  prevent 
overheating.  It  would  be  better  economy  to  use  the  heavy  oil 
on  these  few  bearings  only,  or  better  still,  to  correct  the  mechan- 
ical conditions  so  that  the  proper  grade  of  oil  can  be  used 
throughout. 

Cooling  Heated  Bearings. — When  small  bearings  heat  up  they 
are  usually  easy  to  cool  down,  as  the  total  amount  of  heat  present 
in  the  bearings  is  not  very  great;  usually  a  liberal  supply  of  the 
oil  in  use  is  all  that  is  required;  if  the  bearing  is  heated  to  such 
an  extent  that  it  has  been  distorted  or  the  white  metal  has  started 
to  flow,  it  must  be  dismantled  and  put  in  thorough  working 
order. 

When  large  bearings  heat  up,  the  case  is  very  different,  as  large 
bearings  may  absorb  and  contain  a  great  deal  of  heat ;  and  when 
once  a  large  journal  starts  heating  and  expanding,  there  is  rela- 
tively so  little  clearance  that  the  oil  film  is  easily  squeezed  out 
and  the  bearing  may  seize.  The  first  thing  to  do  when  a  large 
bearing  heats  up  is  therefore  to  increase  the  bearing  clearance 
by  slacking  back  the  bearing  brasses. 

If  the  bearing  has  not  seized  but  only  is  extremely  hot,  it  is 
usually  sufficient  to  feed  the  bearing  with  a  liberal  supply  of 
steam  cylinder  oil  (which  possesses  superior  lubricating  properties 
under  high  temperature)  until  the  bearing  cools,  when  gradually 
the  normal  practice  of  oiling  the  bearing  can  be  re-instated. 

If  the  bearing  has  commenced  to  seize,  a  little  graphite,  talc, 
flower  of  sulphur,  white  lead,  salt,  sapolio,  or  like  ingredients 


BEARINGS  123 

mixed  with  cylinder  oil,  may  be  used,  as  these  solid  ingredients 
help  to  smooth  down  the  parts  that  have  started  to  cut,  thus 
enabling  the  cylinder  oil  to  form  a  film.  Even  more  drastic 
"remedies"  like  brick  dust  or  grindstone  dust  have  been  known 
to  cool  bearings,  when  more  greasy  ingredients  failed  to  separate 
the  surfaces. 

Castor  oil  is  often  employed  for  cooling  bearings,  but  should  be 
avoided  where  a  circulation  system  is  employed,  because  it 
mixes  with  the  engine  oil,  and  afterward  develops  deposits. 
Once  a  bearing  has  become  accustomed  to  the  use  of  castor  oil 
it  is  not  always  a  simple  matter  to  change  back  to  the  original 
conditions. 

The  practice  of  using  water  for  cooling  the  bearings  from  the 
outside  is  very  undesirable,  as  the  result  of  the  sudden  cooling 
is  nearly  always  distortion  of  the  bearing  brasses,  so  that  they 
have  to  be  filed  and  scraped  before  satisfactory  operation  can 
again  be  expected. 

LUBRICATION 

The  object  of  bearing  lubrication  is,  firstly,  to  form  a  lubricat- 
ing film  between  the  rubbing  surfaces  and  thus  replace  the  metallic 
friction  with  fluid  friction,  as  far  as  possible;  secondly,  to  reduce 
the  fluid  friction  in  the  oil  film  itself  to  the  lowest  safe  point,  con- 
sidering the  operating  conditions. 

No  Lubrication. — If  a  journal  revolves  in  its  bearing  without 
lubrication,  metallic  contact  will  cause  abrasion  of  the  metal  and 
the  bearing  will  not  operate  very  long  before  the  frictional  heat 
developed  will  be  so  great  that  the  bearing  surfaces  will  be 
destroyed. 

Oil-less  bearings  are  an  exception;  they  are  made  of  some  metal 
alloy  or  compressed  wood,  mixed  with  graphite,  talc  or  other 
solid  lubricant;  or  the  graphite  is  firmly  placed  in  the  bearing  in 
the  form  of  spiral  grooves  or  strips,  or  again,  the  whole  bearing 
may  be  compressed  talc,  soapstone  or  graphite.  Such  bearings 
will  often  run  without  lubrication,  and  without  seizure,  but  the 
friction  is  very  high  as  also  the  bearing  temperature. 

Semi-lubrication. — By  introducing  a  lubricating  medium  be- 
tween the  rubbing  surfaces,  the  lubricant  will  adhere  to  the  jour- 
nal, as  well  as  to  the  bearing,  thus  replacing  part  of  the  metallic 
friction  with  fluid  friction;  there  will  be  less  abrasion,  therefore 
less  wear,  friction  and  heat. 

The  vast  majority  of  bearings  are  semi-lubricated,  i.e.,  the 
rubbing  surfaces  are  never  kept  completely  apart,  so  that  more 
or  less  wear  does  occur,  and  the  loss  in  friclion  is  not  so  low  as  it 
might  be. 


124  PRACTICE  OF  LUBRICATION 

As  all  fixed  oils  are  more  oily  than  mineral  oils,  an  admixture 
of  a  few  per  cent,  to  the  mineral  oil  will  increase  its  oiliness  and 
assist  in  separating  the  rubbing  surfaces  more  completely. 

If  it  were  not  for  the  high  price  of  fixed  oils  and  their  tendency 
to  gum  (particularly  the  vegetable  oils)  they  ought  to  be  much 
more  widely  used  than  is  the  case  at  present.  It  is  particularly 
for  heavy  pressures  and  slow  speed  that  great  oiliness  is  so  very 
desirable,  necessitating  the  use  of  fixed  oils.  It  is  a  well-known 
fact  that  castor  oil  and  rape  oils  are  extremely  useful  for  very  severe 
conditions  of  this  kind. 

Compounded  oils  also  have  the  property  of  combining  and 
emulsifying  with  water,  so  that  their  use  is  desirable  where  water 
gains  access  to  the  bearings.  Water  will  displace  a  straight 
mineral  oil  and  cause  trouble,  but  will  combine  with  a  com- 
pounded oil  and  form  an  emulsion  or  lather,  which  particularly 
in  the  case  of  marine  steam  engines,  is  very  desirable.  If  a 
bearing  under  such  conditions  heats  up,  the  lather  escaping 
from  the  bearing  will  lose  its  milky  appearance  and  become 
semi-transparent,  this  being  an  indication  of  excessive  bearing 
heat. 

Compare  remarks  under  textile  machinery,  marine  steam 
engines,  locomotives,  stainless  oils,  etc. 

Oil  Film  Lubrication. — By  introducing  a  sufficient  quantity  of 
oil  it  is  possible  to  form  between  the  rubbing  surfaces  a  complete 
oil  film,  which  means  that  there  will  be  no  wear,  and  that  the 
friction  developed  is  reduced  entirely  to  the  fluid  friction 
within  the  oil  itself.  Given  the  necessary  surface  speed,  a 
iiiitable  bearing  pressure  and  the  required  flow  of  oil,  as  will 
often  be  the  case  with  circulation  oiling,  ring  oiling  and  bath 
oiling  systems,  the  friction  is  entirely  fluid  friction  determined  by 
the  viscosity  of  the  oil,  the  surface  speed  and  the  area  of  the  rub- 
bing surfaces;  oiliness  is  of  no  importance  (except  when  starting 
and  stopping);  it  is  the  viscosity  alone  which  maintains  the  oil 
film.  The  higher  the  viscosity  the  more  easily  will  the  film  be 
formed  at  low  speeds;  but  at  high  speeds,  high  viscosity  oils  may 
give  trouble  and  low  viscosity  oils  should  always  be  preferred. 

Michell  thrust  bearings  operate  with  perfect  film  formation, 
see  page  170,  and  Michell  has  also  applied  this  same  principle 
to  journals. 

SELECTION  OF!  OIL 

In  order  to  obtain  efficient  lubrication  oils  must  be  selected  to 
suit  the  operating  conditions  and  the  oiling  system  employed. 


BEARINGS  125 

Operating  Conditions. — As  mentioned  under  "Operating  Con- 
ditions" the  oil  must  be  selected  to  suit  the  conditions  of  size, 
speed,  pressure,  temperature  and  mechanical  conditions. 

Speaking  generally,  oils  light  in  body  should  be  employed  for 
such  conditions  as  small  bearings,  high  surface  speed,  low  bearing 
pressure,  low  room  temperature,  and  good  mechanical  conditions. 

Speaking  generally,  oils  heavy  in  body  should  be  employed  for 
large  bearings,  low  surface  speed,  high  bearing  pressure,  high 
room  temperature,  and  bad  or  indifferent  mechanical  conditions. 

Oiling  Systems. — The  oil  must  also  be  selected  to  suit  the 
oiling  system  employed. 

Hand  Oiling. — Hand  oiled  bearings  are  rarely  well  lubricated; 
they  are  usually  only  semi-lubricated  and  demand  the  use  of 
heavier  bodied  oils  than  would  be  required  with  a  more  efficient 
oiling  system.  This  system  wastes  both  oil  and  power.  Unless 
the  waste  of  oil  is  very  abnormal  compounded  oils  should  be 
preferred  for  hand  oiling,  as  such  oils  have  greater  oiliness  than 
straight  mineral  oils,  therefore  last  longer  and  give  less  friction. 

Drop-feed  Oiling. — In  drop-feed  oiled  bearings  less  oil  is  wasted 
than  in  hand  oiled  bearings,  and  owing  to  the  more  regular  oil 
feed,  the  oil  film  in  the  bearings  is  kept  more  uniform  and  more 
complete;  the  lubrication  is  therefore  more  efficient,  i.e.,  there  is 
less  friction  and  less  wear.  Under  high  pressure  conditions  com- 
pounded oils  should  preferably  be  used;  for  low  or  moderate 
pressures  straight  mineral  oils  will  render  good  service. 

Ring  Oiling. — By  the  ring  oiling  system  the  bearing  surfaces 
are  constantly  flooded  with  oil,  so  that  the  lubrication  be- 
comes as  efficient  as  possible  with  the  particular  grade  of  oil 
in  use.  Straight  mineral  oils  should  be  used,  as  compounded 
oils  will  cause  gumminess  on  the  oil  rings  and  in  the  bearings. 

Splash  Oiling. — The  oil  should  be  light  in  body  so  as  to  splash 
easily  to  all  parts,  yet  sufficiently  heavy  in  body  to  produce 
satisfactory  lubrication. 

Circulation  Oiling. — As  the  oil  is  forced  in  large  quantities  to 
the  bearings,  the  oil  is  given  every  assistance  to  produce  complete 
and  perfect  lubrication,  and  the  heat  is  so  rapidly  removed  that  it 
becomes  possible  to  operate  engines  employing  this  system  at  the 
highest  speeds  and  yet  maintain  a  great  margin  of  safety  in  opera- 
tion. The  oil  must,  however,  be  of  such  a  character  as  to  main- 
tain its  nature,  notwithstanding  that  it  circulates  continuously 
and  is  exposed  to  the  oxidizing  influence  of  air  and  impurities, 
the  emulsifying  influence  of  water,  etc.  Also,  the  oil  must  be  of 
such  a  nature  as  to  separate  quickly  from  water  and  impurities, 
so  that  sludge  or  deposit  developed  may  be  easily  removed  from 


126  PRACTICE  OF  LUBRICATION 

the  oil  in  circulation.  As  to  the  nature  of  such  oils — circula- 
tion oils — see  remarks  under  "  Turbine  Lubrication,"  page  235. 

The  best  oils  used  in  splash  oiling,  ring  oiling  or  oil  bath  systems 
possess  similar  characteristics. 

Where  hand  oiling  or  drop-feed  oiling  systems  are  employed, 
the  oil,  after  passing  through  the  bearings  once,  is  frequently  run 
to  waste  and  not  used  over  again,  in  which  case  the  slight  altera- 
tion which  takes  place  in  the  oil  passing  through  the  bearing  is  of 
no  importance  and  compounded  oils  can  be  used  without  trouble. 

When  the  oil,  after  passing  through  the  bearings,  is  collected 
and  filtered  for  the  purpose  of  using  it  over  again,  either  on  the 
same  bearings  or  for  less  important  work,  mineral  oil  may  be 
preferred,  particularly  if  it  be  used  over  and  over  again  a  great 
number  of  times  on  important  bearings  and  with  only  slight  loss. 

Selection  of  Oil. — It  will  now  be  understood  that  when  select- 
ing oils  for  bearings  operating  at  high  speed,  with  low  bearing 
pressures,  and  employing  a  good  lubricating  system,  the  chief 
object  should  be  to  reduce  the  fluid  frictional  losses,  as  here  the 
question  of  wear  is  less  apt  to  become  an  important  factor. 

For  high-speed  spindles  in  textile  mills,  high-speed  shafting 
and  machinery  of  many  types,  oils  of  the  correct  light  body  and 
quality  should  therefore  be  selected,  and  the  result  will  be  an 
appreciable  reduction  in  power. 

In  bearings  operating  at  slow  speed,  with  heavy  bearing  pres- 
sures and  using  a  less  efficient  oiling  system,  the  danger  of  wear  is 
great,'  and  the  chief  object  of  lubrication  here  becomes  minimiza- 
tion of  wear,  rather  than  the  reduction  of  fluid  friction. 

For  such  bearings  as  are  employed  in  large  open  type  steam 
engines,  heavy  pumping  plant,  heavy  machinery  bearings,  oils  of 
the  correct  heavy  body  and  qualtity  should  be  selected. 

There  are  many  plants  in  which  it  is  declared  that  there  is  no 
trouble.  Whether  this  be  so  or  not,  there  is  a  long  distance  from 
this  no-trouble  standpoint  to  perfection  in  operation;  it  is  only 
by  analyzing  the  actual  conditions,  carefully  grouping  various 
portions  of  the  machinery,  and  using  specially  selected  oils  for 
each  group  to  give  maximum  lubrication  service,  that  perfect 
results  can  be  obtained  and  maintained. 

There  are  many  types  of  modern  machinery,  such  as  steam 
turbines,  high-speed  steam  engines,  and  internal  combustion 
engines  of  all  kinds  and  other  high-speed  machinery,  where  the 
conditions  demand  the  use  of  the  highest  quality  oil  obtainable, 
almost  regardless  of  its  cost,  and  where  smooth  and  safe  operation 
and  low  frictional  losses  count  many  times  more  than  the  cost  of 
the  oil  itself.  On  the  other  hand,  where  the  class  of  machinery 


BEARINGS  127 

in  use  is  rough  or  in  bad  repair,  where  wasteful  and  inefficient 
oiling  systems  are  employed,  and  particularly  where  the  care  and 
attention  given  to  the  plant  are  indifferent  or  bad,  it  is  not  always 
possible  to  justify  the  use  of  the  best  quality  lubricating  oils. 
So  much  oil  may  be  wasted  to  no  useful  purpose,  that  the  cost  of 
the  oil  thus  literally  thrown  away  will  more  than  outweigh  the 
value  of  the  better  lubrication  which  might  be  brought  about 
by  the  use  of  better  oils. 

BEARING  OILS 

To  satisfy  the  bearing  requirements  of  the  great  variety  of 
engines  and  machinery  in  existence,  a  great  number  of  bearing- 
oils  are  needed.  Many  of  these  oils  will  be  mentioned  under  the 
class  of  machinery  for  which  they  are  recommended,  such  as*: 

CIRCULATION  OILS For  steam  turbines,  enclosed  type  steam 

engines,  etc. 
MARINE  ENGINE  OILS For  marine   steam    engines   and   other 

severe  service. 
Loco  ENGINE  AND  CAR  OILS.  . .  .   For  locomotives,  tenders  and  cars. 

SPINDLE  AND  LOOM  OILS For  textile  machinery. 

BLACK  OILS For  mine  cars  and  rough  machinery. 

STEAM  CYLINDER  OILS Used  for  bearing  lubrication  of  enclosed 

type,  splash  oiled  steam  engines. 

In  all  these  cases  there  are  service  conditions  which  call  for 
some  special  property  in  the  oil,  and  therefore  justify  grouping 
such  bearing  oils  in  the  way  indicated  above. 

With  bearing  oils  the  author  proposes  to, refer  to  oils  intended 
to  be  used  and  recommended  for  all  types  of  machinery,  where  the 
service  conditions  do  not  present  any  specially  difficult  features. 

In  other  words,  bearing  oils  are  oils  whose  prime  duty  it  is  to 
lubricate  and  which  are  not  required  to  withstand  oxidation  or 
emulsification  (as  circulation  oils),  or  to  lubricate  heavy  bearings 
in  the  presence  of  water  (as  loco  and  marine  engine  oils),  or  to 
possess  stainless  properties  (as  loom  oils),  etc. 

Bearing  oils  are  oils  ranging  in  color  from  light  red  to  deepest 
red;  they  must  be  refined  but  need  not  be  specially  well  refined; 
in  fact,  excessive  acid  treatment  or  earth  filtration  removes  many 
ac.tive  unsaturated  hydrocarbons,  some  of  which  are  quite  as 
good  if  not  better  lubricants  than  the  saturated  hydrocarbons. 

A  certain  degree  of  refining  is,  of  course,  needed  to  remove  a 
sufficient  amount  of  the  most  unsaturated  elements  which,  if 
left  in  the  oil,  would  cause  excessive  gumming  in  the  bearings. 

The  oiliness  of  distilled  mineral  lubricating  oils  can  be  improved 
by  admixture  of  a  small  percentage,  say  from  5  per  cent,  to  10 
per  cent,  of  fixed  oil,  or  a  certain  percentage  of  filtered  cylinder 


128 


PRACTICE  OF  LUBRICATION 


stock.  To  make  this  point  clearer,  the  author  has  found  that 
when  using  oils  compounded  in  this  manner  (i.e.,  admixture  of 
fixed  oil  or  filtered  cylinder  stock)  lower  viscosity  oils  can  be 
selected  to  render  certain  service,  than  if  a  distilled  mineral  lubri- 
cating oil  were  to  be.  employed;  the  result  is  therefore,  lower 
friction  and  wear. 

Such  savings  in  power  accomplished  by  using  lower  viscosity 
compounded  oils  are  mentioned  page  318  for  textile  machinery. 
In  the  same  way,  power  savings  can  be  obtained  by  replacing  a 
distilled  mineral  oil  of  a  certain  viscosity  by  a  lower  viscosity  oil, 
which  is  made  by  mixing  a  spindle  oil  (or  a  blend  of  a  spindle  oil 
and  a  medium  red  oil)  with  a  certain  amount  of  filtered  cylinder 
stock. 

Without  going  more  deeply  into  this  matter,  the  author  gives 
below  approximate  Saybolt  viscosities  at  104°F.  for  six  bearing- 
oils,  which  will  be  found  to  cover  a  wide  range  of  service. 

LUBRICATION  CHART  No.  1,  FOR  BEARINGS 


Saybolt 
viscosity  at 
104°F.,  seconds 

Recommended  for 

Bearing  oil  No.  1  
Bearing  oil  No.  2  

Bearing  oil  No.  3 

95 
120 

175 

Very  light  duty  and  high  speed. 
Light  or  medium  duty  and  medium 
or  high  speed. 
Medium  duty  and  medium  or  high 

Bearing  oil  No.  4  
Bearing  oil  No.  5  
Bearing  oil  No.  6 

250 
450 
700 

speed. 
Medium  or  heavy  duty  and  medium 
or  high  speed. 
Heavy   duty   and   slow   or  medium 
speed. 
Heavy  duty  and  slow  speed. 

The  author  hesitates  to  give  the  above  service  recommenda- 
tions which  of  necessity  are  very  crude,  but  under  the  various 
sections  of  engines  and  machinery  following  this  chapter  he  has 
endeavored  to  convey  his  ideas  and  experience  in  a  more  definite 
manner. 

SEMI-SOLID  LUBRICANTS 

The  various  methods  by  which  semi-solid  lubricants  are  applied 
may  be  classified  as  follows : 

Contact  feed 
Stauffer  cups 
Compression  cups 
Mechanical  feed 
Grease  bath. 


BEARINGS 


129 


Contact  Feed. — By  this  method  the  grease  is  placed  direct  on 
the  journal,  as,  for  example,  in  the  dryer  bearings  of  paper  ma- 
chines, the  roll  neck  bearings  in  steel  mills,  etc.  The  grease 
adheres  to  the  journal,  melts  away  or  softens  and  gradually 
wears  away.  Hard  greases  are  generally  employed.  With 
soft  greases  the  consumption  is  usually  great,  particularly 
when  the  bearing  is  worn  as  in  that  case  the  grease  adhering  to 
the  journal  is  pulled  into  the  large  clearing  space  between  the 
journal  and  the  keep  and  is  quickly  consumed. 

When  soft  grease  is  applied  direct  to  the  shafting  it  must  be 
protected  by  a  layer  of  yarn  fibre  grease,  as  for  example  in  shaft- 
ing bearings  for  weaving  sheds  and  in  bearings  used  in  connec- 
tion with  the  rollers  which  support 
rotary  kilns  in  cement  works. 
Such  bearings  have  a  large  cavity 
at  the  top  (Fig.  23);  the  yarn 
grease  is  placed  all  around  the 
walls  of  this  cavity  and  sometimes 


FIG.  23. — Contact  grease  feed  arrange- 
ment. 


FIG.  24. — Gravity  grease  feed 
arrangement. 


also  there  is  a  bottom  layer  touching  the  journal.  In  the  pocket 
thus  formed  is  placed  ordinary  cup  grease  or  fibre  grease,  the 
grade  being  selected  in  accordance  with  the  temperature  condi- 
tions; exposed  to  the  heat,  the  grease  in  the  pocket  melts  slowly 
through  the  yarn  grease  and  lubricates  the  journal. 

Fig.  24  shows  a  gravity  feed  grease  cup  designed  for  the  use 
of  low  melting  point  greases  or  oils  which  are  slightly  soap- 
thickened,  so  as  to  be  non-fluid  at  ordinary  room  temperatures. 

The  needle,  in  touching  the  shafting  gets  warm,  melts  a  little 
of  the  grease  and  acts  very  much  like  the  needle  in  glass  bottle 
oilers  (Fig.  19,  page  109). 

Stauffer  Cups. — Fig.  25  shows  an  ordinary  plain  cup;  the 
bottom  is  preferably  sloping  to  facilitate  the  grease  being  forced 


130 


PRACTICE  OF  LUBRICATION 


out  of  the  cup.  The  cover  is  given  an  occasional  turn  and  a 
quantity  of  grease  is  forced  into  the  bearing;  it  is  gradually  con- 
sumed until  the  cover  is  given  another  turn.  To  prevent  thin 
.grease  from  leaking  out,  the  thread  must  be  a  good  fit  or  a  leather 
packing  must  be  introduced  as  shown  in  Fig.  26.  This  drawing 
also  shows  a  catch-pawl  which  prevents  the  cover  from  slacking 

back. 

Compression  Cups. — Compres- 
sion cups  may  be  operated  either 
by  a  spring  or  by  compressed  air. 
Fig.  27  shows  a  typical  spring  com- 
pression cup.  The  spring  (1) 
pushes  against  the  piston  (2). 
The  feed  can  be  adjusted  by  the 
screw  (3).  Only  greases  of  No.  1  and  No.  2  consistency  can  be 
used  in  this  type  of  cup. 

For  harder  greases  of  No.  3  or  No.  4  consistency,  a  grease  cup 
must  be  used  like  Phillips  crank  pin  grease  cup  shown  in  Fig.  28. 
By  turning  the  milled  collar  (1)  grease  is  forced  up  into  the  small 
cylinder  (2)  raising  the  piston  against  the  force  of  a  strong  spring, 


FIGS.  25-26. — Stauffer  cups. 


FIG.     27. — Spring    com- 
pression cup. 


FIG.    28. — Phillips    crank     FIG.   29. — Menno  grease 
pin  grease  cup.  cup. 


which  subsequently  feeds  the  grease  until  the  indicator  knob  (3) 
shows  that  another  feed  must  be  given. 

Fig.  29  illustrates  the  Menno  compressed  air  cup  in  which 
compressed  air  is  employed  for  forcing  out  the  lubricant.  The 
lubricant  is  filled  into  the  bottom  portion  (1)  of  the  cup;  this 
part  is  threaded  to  receive  the  upper  portion  (2)  which  on  being 
screwed  into  the  lower  portion  causes  a  certain  air  pressure  to  be 
formed  above  the  grease.  The  object  of  the  thin  metal  disc  (3) 


BEARINGS 


131 


which  is  guided  vertically  is  merely  to  rest  on  top  of  the  grease 
and  keep  it  level.  The  fixed  disc  (4)  forms  the  top  of  the  air 
compression  chamber.  After  giving  the  upper  portion  (2)  a 
certain  number  of  turns,  it  is  locked  to  the  bottom  portion  by 
means  of  a  lock  nut  (5)  and  the  air  pressure  will  maintain  a  fairly 
regular  feed.  If  the  journal  gets  warm,  the  heat  is  conducted 
up  into  the  cup  through  a  thin  funnel.  The  effect  of  this  rise  in 
temperature  is  to  soften  the  grease,  increase  the  air  pressure, 
and  give  an  increased  feed  of  lubricant. 

In  grease  cups  for  lubricating  loose  pulleys  the  centrifugal 
force  acting  on  a  piston  may  be  made  use  of  to  force  thin  grease, 
or  non-fluid  oil,  to  the  bearing. 

Mechanical  Feed. — In  very  large  colliery  winding  engines  or 
steel  works  rolling  mill  engines,  hard  greases,  usually  white 


1  Couuccting  Rod 

2  Crauk  Pin  Bearing 

3  Driving  Cam 
i  Ratchet  Lever 

5  Ratchet 

6  Worm  Wheel 

7  Piston 

8  Grease 

'.»  Grease  Feeding  Pipe 


FIG.  30. — Mechanical  grease  lubricator. 

greases,  may  be  forced  into  the  crank  pins  by  means  of  mechan- 
ically operated  lubricators  as  indicated  in  the  sketch  (Fig.  30). 

The  arrangement  is  very  similar  to  the  banjo  oiler.  A  cam 
on  the  feed  pipe  (3)  operates  a  ratchet  lever  (4).  The  motion  of 
the  ratchet  wheel  (5)  and  worm  gear  (6)  actuates  a  piston  (7), 
which  forces  the  grease  be  ow  the  plunger  through  the  feed  pipe 
(9)  into  the  crank  pin.  Another  method  is  to  place  the  lubri- 
calor  complete  on  the  crank  pin  itself.  The  lever  (4)  is  then 
weighted  at  its  lower  end  and  swings  to  the  right  and  left 
between  two  adjustable  stops,  owing  to  the  motion  of  the  crank 
pin.  The  lever  in  this  way  oscillates  sufficiently  to  operate  the 
ratchet,  and  the  feed  may  be  adjusted  within  certain  limits,  say, 
1,  2  or  3  teeth  per  revolution. 

The  advantage  of  a  mechanical  feed  as  against  compression 


132  PRACTICE  OF  LUBRICATION 

cups  is  that  the  lubricant,  whether  soft  or  hard,  is  delivered  ab- 
solutely uniformly,  notwithstanding  changes  in  temperature  which 
either  harden  or  soften  the  grease  and  the  result  of  which  with  ordi- 
nary grease  cups  is  that  a  uniform  feed  cannot  be  maintained. 

Grease  Bath. — A  bath  of  grease  may  be  employed  in  con- 
nection with  ball  and  roller  bearings,  gear  boxes  of  automobiles, 
gear  chambers  in  pneumatic  tools,  etc. 

The  reasons  why  grease  is  employed  are  outlined  under  these 
several  headings  and  are  mainly  to  keep  dust  or  grit  out  of  bear- 
ings or  to  prevent  excessive  leakage  of  lubricant. 

Greases  of  Nos.  1  and  2  consistencies  are  used  for  grease  baths; 
harder  greases  create  undue  friction,  are  inclined  to  cake  exposed 
to  heat,  and  do  not  distribute  themselves  with  sufficient  ease. 

GREASE  LUBRICATION  IN  GENERAL 

The  conditions  for  which  semi-solid  lubricants  are  advantage- 
ously employed  will  be  indicated  in  the  following,  fuller  infor- 
mation being  given  under  the  various  sections  of  machinery, 
etc.,  referred  to. 

In  dusty  and  dirty  surroundings,  e.g.,  cement  mills,  bakeries, 
colliery  screening  plants,  etc.,  grease  keeps  the  bearings  clean; 
it  entirely  fills  the  bearing  cavities  and  the  clearance  space  and 
forms  a  fillet  round  the  bearing  ends,  which  prevents  the  entrance 
of  dust  and  dirt.  This  is  particularly  important  for  ball  and 
roller  bearings. 

When  oil  is  used  in  weaving  sheds,  it  is  necessary  to  fix  savealls 
below  the  bearings.  For  this  reason  grease  is  sometimes  preferred 
to  oil,  because  there  is  less  likelihood  of  the  spent  lubricant 
dropping  from  the  bearings  on  to  the  looms  and  soiling  the  goods. 

When  bearings  are  in  inaccessible  places  and  cannot  be  lubri- 
cated with  oil  by  ordinary  means,  grease  cups  can  be  fitted,  and 
the  grease  forced  through  tubes  into  the  bearings  from  any  angle. 

Greases  of  high  melting  point — fibre  greases  and  other  greases — 
are  required  occasionally  where  the  bearing  temperatures  or  room 
temperatures  are  unusually  high,  such  as  the  hot  necks  on  dryers 
in  paper  mills,  hot  journals  supporting  the  rotary  kilns  in  cement 
works,  hot  roll  necks  in  tin-plate  mills  and  steel  mills,  etc. 

Grease  should  be  used  only  where  there  are  special  reasons 
against  the  use  of  oil.  Wherever  grease  is  used  under  conditions 
that  are  quite  suitable  for  oil  lubrication,  the  introduction  of  the 
correct  grade  of  oil  will  always  result  in  an  appreciable  saving  in 
power.  Grease  lubrication  means  a  heavy  frictional  resistance  in 
the  bearings,  as  obviously  the  grease  does  not  commence  to 
lubricate  until  the  frictional  temperature  has  increased  to  such 


BEARINGS  133 

an  extent  that  the  grease  melts  or  becomes  sufficiently  soft  to  be 
" abraded"  by  the  revolving  journal. 

The  suitability  of  a  grease  depends  on  four  things : 

1.  The  purity  of  the  grease  and  the  absence  of  filling  matter. 

2.  The  consistency  of  the  grease  (to  suit  the  method  of  appli- 
cation). 

3.  The  quality  of  the  oil  and  other  ingredients  in  the  grease. 

4.  The  melting  point  of  the  grease  (to  suit  the  temperature 
conditions). 

Purity  is  very  important  in  greases  which  are  used  under  con- 
ditions of  high  pressure  or  speed.  Such  greases  should  prefer- 
ably be  strained  hot  as  mentioned,  page  25. 

Filling  matter  is  non-lubricating;  it  lowers  the  manufacturing 
cost  of  grease,  but  usually  detracts  from  its  lubricating  value. 
For  rough  mechanical  conditions  or  for  very  high  bearing  pres- 
sures and  slow  speed,  filling  matter  like  graphite,  talc,  or  mica 
may,  however,  prove  advantageous,  helping  to  fill  up  unevenness 
in  the  rubbing  surfaces  and  preventing  seizure.  Filling  matter, 
containing  gritty  or  hard  impurities  will  cause  wear,  but  may 
prove  beneficial  as  a  temporary  remedy  in  the  case  of  hot  bearings 

Consistency. — The  consistency  of  grease  is  largely  governed 
by  the  feeding  appliances.  If  grease  is  applied  through  com- 
pression cups  or  gravity  feed  cups  it  must  be  soft,  either  No.  1 
or  No.  2  consistency,  also  when  used  for  high  speed  bearings, 
ball  and  roller  bearings. 

For  Stauffer  cups,  No.  2,  No.  3  or  No.  4  consistency  can  be 
employed. 

A  grease  of  No.  4  or  No.  5  consistency  may  be  selected  for 
contact  feed  application  in  connection  with  slow  speed  open 
bearings,  the  grease  resting  direct  on  the  rotating  shaft. 

Quality. — The  quality  of  grease  depends  largely  on  the  quality 
of  the  lubricating  oil  used  in  manufacture. 

For  medium  and  high-speed  work,  with  no  excessive  bearing 
pressures,  a  grease  should  be  chosen  which  contains  a  light- 
bodied  lubricating  oil. 

For  medium  and  slow-speed  work  with  fairly  heavy  bearing 
pressures,  the  grease  should  preferably  contain  a  more  viscous 
oil;  and  for  extreme  conditions  of  pressure  and  slow-speed,  fatty 
oils  or  fats  must  form  part  of  the  grease,  as  great  oiliness  is 
required.  A  percentage  of  solid  lubricants  may  also  be  of  advan- 
tage as  mentioned  under  "  Filling  Matter." 

Changing  Grease. — When  a  change  is  made  from  white  and 
other  greases  which  contain  much  tallow  or  other  fat  or  fatty 
oils  to  a  mineral  grease,  as  cup  grease,  the  process  must  be 


134  PRACTICE  OF  LUBRICATION 

gradual  to  avoid  heating,  this  being  just  as  necessary  as  when 
changing  from,  say,  castor  oil  to  a  mineral  oil. 

SOLID  LUBRICANTS 

In  order  to  determine  the  proper  range  of  service  for  the  various 
solid  lubricants  in  the  field  of  lubrication,  the  subject  will  be 
divided  into  the  following  sections: 

THE  ACTION  OF  SOLID  LUBRICANTS 

METHODS  OF  APPLICATION  AND  USE 

OBSERVATIONS  ON  RESDLTS  OBTAINED  BY  THE  USE  OF  SOLII>LUBUICANTS. 

In  order  to  avoid  having  to  refer  repeatedly  to  the  use  of  solid 
lubricants  throughout  the  book  the  Author  has  at  this  place  dealt 
with  the  entire  field  of  service  for  solid  lubricants  in  such  a  man- 
ner that  further  references  to  this  subject  may  perhaps  be  con- 
sidered unnecessary. 

THEORY  OF  THE  ACTION  OF  SOLID  LUBRICANTS 

It  is  generally  agreed  that  the  friction  created  in  engines  or 
machinery  of  all  kinds  is  chiefly  composed  of  what  may  be  termed 
solid  friction  or  fluid  friction,  or  a  combination  of  both;  the  latter 
condition  representing  the  state  of  affairs  in  the  great  majority 
of  cases. 

In  the  following  the  influence  of  solid  lubricants  on  each  of 
these  various  kinds  of  friction  will  be  dealt  with  separately. 
Reference  will  also  be  made  to  the  use  of  solid  lubricants  for 
treatment  of  hot  bearings. 

Solid  Lubricants  and  Solid  Friction. — When  a  solid  lubricant  is 
introduced  between  otherwise  unlubricated  surfaces,  the  more  or 
less  finely  divided  particles  of  the  lubricant  associate  themselves 
with  one  or  other  of  the  rubbing  surfaces,  filling  in  the  pores  and 
depressions  and  acting,  as  far  as  possible,  as  a  smoothing  and 
polishing  agent,  covering  the  original  surfaces  with  a  thin  smooth 
layer  of  the  solid  lubricant.  As  a  result,  the  coefficient  of  fric- 
tion is  reduced;  the  solid  friction  between  the  more  or  less  rough 
original  rubbing  surfaces  is  replaced  by  the  lesser  solid  friction 
between  the  smooth  surfaces  formed  by  the  solid  lubricant. 

When  abrasion  takes  place,  it  occurs  not  so  much  between  the 
original  surfaces  (which  possess  great  cohesion)  as  between  the 
particles  of  the  solid  lubricant  which  have  but  little  cohesion. 
Artificial  amorphous  graphite,  for  example,  has  practically  no 
cohesion.  If  solid  lubricants  are  employed,  cutting  and  abrasion 
of  the  bearing  surfaces  are  therefore  much  less  likely  to  occur. 


BEAR1NCS  135 

There  are  a  variety  of  conditions  for  which  dry  solid  lubricants 
have  proved  advantageous,  as  for  example,  in  bearings  or  in 
such  parts  of  machinery  as  are  apt  to  be  neglected  from  a  lubri- 
cating point  of  view,  and  which  operate  at  low  pressures  and  low 
speeds.  When  such  surfaces  are  well  coated  with  graphite,  for 
example,  and  particularly  if  they  are  rubbed  down  to  a  dense 
glazed  finish,  they  will  work  upon  each  other  for  a  long  time  with 
comparative  freedom  and  without  danger  of  cutting  or  wear 
taking  place. 

Solid  Lubricants  and  Fluid  Friction. — The  application  of 
solid  lubricants  to  bearings  in  which  a  perfect  oil  film  is  estab- 
lished would  at  first  sight  appear  to  be  of  no' value;  the  journal 
floats  on  a  film  of  oil  and  the  presence  of  small  particles  of  a  solid 
lubricant  does  not  increase  the  viscosity  to  any  appreciable 
extent.  The  friction  under  running  conditions  is  therefore  not 
increased  unless  the  solid  lubricant  is  present  in  such  an  amount 
that  the  particles  " crowd"  the  oil  film  at  the  "point  of  nearest 
approach"  between  journal  and  bearing,  and  commence  to  act 
as  an  abrasive  powder. 

It  has  repeatedly  been  noticed  in  experimental  work  that 
immediately  after  a  temporary  application  of  solid  lubricant  in 
powder  form  the  friction  is  much  increased,  but  is  reduced  after- 
ward, when  the  particles  have  had  time  to  attach  themselves  to 
the  rubbing  surfaces  and  form  a  smooth  coating.  The  virtue 
in  the  employment  of  a  solid  lubricant  lies  entirely  in  the  effect 
it  produces  on  the  rubbing  surfaces  themselves.  With  perfectly 
lubricated  bearings  the  chief  advantage  of  using  a  solid  lubricant 
is  apparently  the  effect  on  the  friction  at  the  moment  of  starting, 
which  results  in  a  reduction  in  the  static  coefficient  of  friction. 

Static  and  Kinetic  Friction. — The  effect  of  the  use  of  a  suitable 
solid  lubricant  or  a  solid  colloidal  lubricant,  is,  as  we  have  seen,  to 
reduce  the  tendency  to  abrasion  and  to  produce  a  smoothness  of 
the  surfaces.  As  the  solid  lubricant  cannot  be  displaced  by  pres- 
sure, the  static  coefficient  of  friction  is  reduced  as  compared  with 
the  result  obtained  when  oil  alone  is  used,  assuming  that  the 
solid  lubricant  is  of  such  a  nature  and  used  in  such  a  manner  that 
it  has  actually  increased  the  smoothness  of  the  rubbing  surfaces. 

Makers  of  the  flake  variety  of  graphite  claim  that  this  type  of 
graphite  lends  itself  better  to  the  production  of  very  smooth  and 
slippery  surfaces  than  the  amorphous  varieties;  in  bearings  with 
rough  or  very  rough  surfaces  the  flakes  adhere  to  one  another  and 
easily  build  up  a  surface.  When  the  bearing  surfaces  are  reason- 
ably well  finished,  this  "  building  up"  action  of  flake  graphite  does 
not  appear  to  be  of  special  value;  in  fact,  it  may  be  detrimental 
where  small  clearances  exist,  particularly  if  fed  in  excess. 


136  PRACTICE  OF  LUBRICATION 

Solid  Lubricants  and  Solid  and  Fluid  Friction. — Under  these 
conditions  there  appear  to  be  great  possibilities  for  the  use  of 
solid  lubricants.  Their  object  will  be: 

(a)  To  reduce  the  solid  friction. 

(6)  To  produce  a  smoothness  of  the  rubbing  surfaces,  which  will  assist 
in  distributing  the  load  evenly  over  all  parts  of  the  bearing  and  thus  enable 
a  lower  viscosity  lubricant  to  be  used  and  the  fluid  friction  to  be  reduced. 

(c)  To  reduce  the  wear  of  the  original  surfaces  and  the  risk  of  abrasion 
or  cutting  of  the  surfaces  which  ordinarily  leads  to  the  production  of  hot 
bearings. 

(d)  To  reduce  the  consumption  of  lubricant. 

To  obtain  these  advantages  the  solid  lubricants  must  be  of 
suitable  nature,  purity,  fineness  and  hardness,  and  must  be  used 
in  the  right  amount. 

Nature. — A  good  solid  lubricant  must  possess  ability  to  adhere 
to  metallic  surfaces  and  it  must  be  capable  of  producing  a  smooth 
surface.  Graphite  possesses  both  of  these  properties  to  a  marked 
degree.  When  rubbed  between  metallic  or  non-metallic  sur- 
faces, graphite  whether  of  the  flake  or  amorphous  variety  pro- 
duces a  coating  which  is  smooth  and  unctuous.  Talc  and  mica  do 
not  adhere  to  surfaces  as  well  as  graphite  does,  nor  do  they  pro- 
duce as  smooth  a  surface. 

The  quality  of  unctuousness  in  the  surface  produced  is  un- 
doubtedly important;  it  is  not  possessed  by  materials  such  as 
flowers  of  sulphur  or  white  lead  which  act  more  as  abrasives  than 
as  lubricants. 

Purity. — A  high  degree  of  purity  of  the  solid  lubricant  is  neces- 
sary in  connection  with  lubrication  of  all  high  class  machinery, 
whereas  for  rough  bearings  operating  under  extreme  conditions 
and  on  the  verge  of  seizure,  a  small  amount  of  impurities  may  not 
be  detrimental. 

L.  Archbutt  has  analyzed  various  samples  of  "Foliac"  flake 
graphites  (Graphite  Products,  Ltd.),  amorphous  graphite  (Dr. 
Acheson's  No.  1340)  and  colloidal  graphites  (Dr.  Acheson's 
aquadag  and  oildag)  as  shown  in  Table  No.  7.  He  makes  the 
following  remarks  with  regard  to  the  colloidal  graphites,  indi- 
cating the  presence  of  the. vegetable  deflocculating  agent: 

"I  have  found  that  it  is  impossible  to  wash  out  the  whole  of  the  oil 
in  'Oildag'  with  ether  and  consequently  the  extracted  graphite  still 
contains  some  oil.  I  have  had  a  similar  experience  in  the  analysis  of 
'Aquadag.'  Although  this  was  very  largely  diluted  and  slightly 
acidified  with  hydrochloric  acid  the  precipitated  graphite  after  filtering 
and  thoroughly  washing  until  perfectly  free  from  chlorides  and  drying 
lost  9  per  cent,  when  heated  in  a  closed  crucible.  On  heating  some 


BEARINGS 


137 


of  this  graphite  in  a  dry  test  tube,  white  fumes  were  given  off  with  a 
smell  of  burning  vegetable  matter,  and  a  brown  oily  distillate  condensed 
on  the  tube." 

TABLE    7. — ANALYSES  OF  LUBRICATING  GRAPHITES,  SUPPLIED  BY  THE 
GRAPHITE  PRODUCTS,  LTD.,  BATTERSEA 


Description 

Foliac 
flake 
graphite 
No.  100 

Foliac 
flake 
graphite 
B.1371 

Foliac 
flake 
graphite 
No.  2 

Foliac 
flake 
graphite 
No.  1 

Foliac 
flake 
graphite 
No.  101 

Moisture 

1.26 

.32 

.20 

.29 

.05 

Further  loss  on  heating 

5  min.  at  faint  redness 

in  closely  covered  cruci- 

ble    "  

.09 

.49 

.42 

.44 

.34 

Mineral  matter  (ash)  .... 

.37 

4.79 

1.93 

9.87 

.05 

Graphite  (by  difference)  . 

98.28 

94.40 

97.45 

89.40 

99.56 

100.00 

100.00 

100.00 

100.00 

100.00 

Composition  of  mineral 

matter: 
Silica 

3.00 

1.06 

4.84 

Alumina  

Mainly 

.67 

.33 

3.32 

Ferric  oxide  .  .  .  .  :  

Ferric 

.86 

.46 

1.55 

Lime,  etc.  (by  difference) 

Oxide 

.26 

.08 

.16 

4.76 

1.93 

9.87 

ANALYSIS  OF  ACHESON  GRAPHITE,  GRADE  No.  1340 

Moisture 07 

Further  loss  on  heating  5  minutes  at  faint  redness 

in  closely  covered  crucible .23 

Mineral  matter  (ash) .66 

Graphite  (by  difference) 99.04 


Composition  of  Mineral  Matter: 

Silica 

Alumina 

.  Ferric  oxide 

Lime,  etc.  (by  difference). .  .  . 


100.00 

.07 
.31 
.25 
.03 

.66 


ANALYSIS  OF  "AQUADAG" 

The  sample  srnelled  distinctly  of  ammonia,  and  was  found  to  contain ; 
Insoluble  in  water  after  coagulation  by  acidifying 

slightly 15.06 

Water  extract  (by  difference; 84 . 94 


100.00 


138 


PRACTICE  OF  LUBRICATION 


Analysis  of  this  gave  the  following  results  : 

Loss  on  heating  5  minutes  at  faint  redness  in 

closely  covered  crucible 9. 12 

Mineral  matter  (ash) 1 . 20 

Graphite  (by  difference) 89 . 68 

100.00 
Composition  of  Mineral  Matter: 

Silica 24 

Alumina .18 

Ferric  oxide .65 

Lime,  etc.  (by  difference) .13 

1.20 
ANALYSIS  OF  "OILDAG" 

Graphite,  etc.,  insoluble  in  ether 11.2 

Ether  extract  (oil) 88 . 8 

100.0 

It  was  found  impossible  to  free  the  graphite  completely  from  oil  by  wash- 
ing with  ether.  Analysis  of  the  "graphite,"  as  extracted,  gave  the  following 
results : 

Loss  on  heating  5  minutes  at  faint  redness  in 

closely  covered  crucible 7.01 

Mineral  matter  (ash) 2 . 25 

Graphite  (by  difference) 90 . 74 

100.00 
Composition  of  Mineral  Matter: 

Silica ;       .21 

Alumina .35 

Ferric  oxide 1 . 02 

Lime,  etc.  (by  difference) .67 

2.25 

For  convenience  of  comparison,  the  above  analyses  have  all 
been  recalculated  on  the  moisture-free  and  volatile  matter-free 
samples,  and  the  results  are  given  below : 


Si 


o  o 


s 


Per  cent,  of  graphite  . 

Per  cent,   of  mineral 

matter  (ash) 


99.34 


98.68 
1.32 


97.58 
2:42 


99.62 
.38 


95.17 
4.83 


98.06 
1.94 


90.06 
9.94 


100.00 


100.00     100.00     100.00 


100.00 


100.00 


100.00 


100.00 


BEARINGS  139 

The  "Foliac  special  large  flake  graphite  No.  101"  is  almost 
chemically  pure.  The  flakes  haye  a  pure  silvery  lustre  when 
reflecting  light;  when  not  reflecting  they  appear  absolutely 
black;  a  little  of  the  graphite  lying  at  the  bottom  of  a  deep 
narrow  trough  of  white  paper  looks  black  and  white,  as  if  it  were 
a  mixture  of  two  substances. 

The  "Foliac"  No.  100  is  apparently  the  same  graphite  as 
No.  101,  ground  very  fine,  and  it  contains  more  impurity,  chiefly 
iron  from  the  mill.  The  "Acheson  graphite  No.  1340,"  though 
of  great  purity,  is  less  pure  than  the  natural  graphite,  and  it  is 
of  interest  to  note  that  the  conversion  of  this  into  "aquadag" 
has  introduced  more  impurity,  and  the  further  conversion  of  this 
into  "oildag"  still  more.  In  all  the  Acheson  graphites  the 
principal  impurities  are  iron  and  alumina.  In  the  "Foliac" 
graphites,  silica  is  the  chief  impurity.  Another  point  to  note, 
which  may  be  of  considerable  importance,  is  the  tenacity  with 
which  the  vegetable  matter  and  oil  used  in  preparing  "  aqua- 
dag  and  "oildag"  cling  to  the  particles  of  graphite  and  cannot 
be  removed  by  solvents." 

Fineness. — In  the  case  of  well  finished  rubbing  surfaces  very 
finely  divided  graphite  must  obviously  be  used,  and  the  coating 
of  the  surfaces  is  easier  to  accomplish  than  with  rough  surfaces. 
Under  these  conditions,  makers  of  amorphous  graphite  claim 
that  a  flake  graphite  when  used  in  excess  is  apt  to  build  up  too 
thick  a  surface  and  reduce  the  working  clearance  to  a  dangerous 
extent,  whereas  with  amorphous  graphite,  excessive  use  can  have 
no  ill  effects;  the  soft  crumbly  amorphous  grains  are  easily 
crushed;  in  fact  a  surface  of  fine  amorphous  graphite  under 
pressure  moves  within  itself  like  a  film  of  oil,  and  the  particles 
are  non-coalescing  and  offer  little  resistance  to  movement. 

With  highly  finished  and  polished  surfaces  operating  with 
small  clearances  it  would  seem  undesirable  to  use  powdered 
lubricants,  however  finely  they  may  be  pulverized.  Colloidal 
lubricants  appear  to  be  the  only  solid  lubricants  likely  to  give 
satisfaction  under  such  conditions. 

The  author  has  examined  Dr.  Acheson's  graphite  No.  1340 
and  the  various  Foliac  flake  graphites  for  fineness,  the  grading 
being  given  in  Table  No.  8.  Foliac  flake  graphite  No.  100  is 
exceedingly  fine,  although  not  so  fine  as  Dr.  Acheson's  No.  1340. 

Note  1. — The  figure  given  for  any  mesh  sieve  means  the  amount 
passing  through  that  sieve  and  retained  on  the  next  sieve,  for 
example: 

Foliac  graphite  No.  1  contains  20  per  cent,  of  particles  passing 
the  30/30  mesh  sieve,  but  too  large  to  pass  the  40/40  mesh  sieve. 


140 


PRACTICE  OF  LUBRICATION 


TABLE  8. — GRADING  OF  GRAPHITES 


Sieve, 
No.  of 
meshes 
per  inch 

Achesou's 
graphite  I 
No.  1340, 
per  cent. 

Foliac  flake 
graphite 
No.  100, 
per  cent. 

Folia6  flake 
graphite 
B.1371, 
1  per  cent. 

Foliac  flake 
graphite 
No.  2, 
per  cent. 

Foliac  flake 
graphite 
No.  1, 
per  cent.  ' 

Foliac  flake 
graphite 
No.  101, 
per  cent. 

10/10 

2.0 

10.0 

20/20 

.... 

15.0 

40.0 

30/30 



.... 

.... 

.... 

20.0 

24.0 

40/40 

1.0 

22.0 

20.0 

50/50 

1.0 

.2 

2.0 

37.0 

6.0 

80/80 

.... 

1.0 

.2 

2.0 

2.0 

100/100 

2.0 

4.0 

36.4 

56.0 

1.0 

200/200 

98.0 

94.0 

63.2 

39.0 

1.0 

Flour...1      95.5 

89.6 

Note  2. — The  per  cent,  of  " Flour"  (impalpable  powder)  is  an 
arbitrary  figure,  determined  by  Petersen's  florometer  which 
consists  of  a  vertical  torpedo-shaped  glass  vessel,  with  a  widest 
diameter  of  4  inches,  4  feet  6  inches  high  with  a  1-inch  opening 
at  the  top  and  drawn  out  to  a  slender  J^-inch  tube  at  the  bottom. 
An  air  current  under  21  mm.  pressure  is  passed  up  through  the 
vessel  for  15  minutes.  Five  grams  of  the  graphite  are  emptied 
into  the  vessel  and  after  the  air  current  is  switched  off,  the  amount 
of  graphite  not  blown  away  is  weighed,  the  percentage  of  flour 
being  thus  easily  determined. 

Hardness. 

HARDNESS  OF  SOLID  LUBRICANTS 


Pure  graphite 

Best  quality  of  talc 

Lower  qualities  of  talc  or  soapstone 

Micas. . 


Relative 
hardness 

1.0 

1.0 

2.5to  4.0 
2.0to3.0 


The  admixture  of  a  hard  solid  lubricant,  like  hard  talc  or  mica, 
to  a  grease,  particularly  if  an  excessive  amount  is  added,  may 
cause  a  great  deal  of  continuous  but  uniform  wear,  much  more 
than  would  be  caused  by  the  grease  used  by  itself,  yet  no  cutting 
or  excessive  heating  of  the  bearing  may  occur. 

Amount. — Makers  of  flake  graphite  recommend  the  admixture 
of  3  per  cent,  to  4  per  cent,  of  fine  flake  graphite  with  oil;  if 
too  much  graphite  be  used,  the  friction  is  increased  because  there 
is  more  graphite  introduced  into  the  bearing  than  is  required  to 
keep  the  rubbing  surfaces  properly  graphited.  The  surplus 
graphite  present  between  the  rubbing  surfaces  creates  extra 
friction  and  heating. 

If  appreciably  less  graphite  is  added  than  3  per  cent,  a  point 


BEARINGS  141 

will  be  reached  when  the  graphite  coating  will  no  longer  be  fully 
maintained  and  the  full  benefits  from  the  use  of  graphite  will  not 
be  obtained. 

Makers  of  graphite  greases  recommend  a  percentage  of  graphite 
ranging  from  3  per  cent,  to  10  per  cent.  More  graphite  is 
required  with  grease  than  with  oil,  because  grease  is  usually 
employed  for  rougher  conditions  than  oil,  and  more  graphite  is 
needed  to  build  up  the  surfaces  and  maintain  them  in  a  smooth 
condition. 

The  effect  of  adding  a  solid  lubricant  to  a  lubricating  grease  is 
that  in  time  the  solid  lubricant  will  attach  itself  to  the  rubbing 
surfaces,  and  by  smoothing  and  polishing  them  will  make  it 
easier  for  the  lubricant  to  do  its  duty.  As  a  result,  a  softer 
grease,  or  a  grease  containing  a  lower  viscosity  oil  can  be  em- 
ployed than  when  no  solid  lubricant  is  added  to  the  grease. 

Makers  of  colloidal  graphite  find  that  a  very  small  percentage 
of  graphite  is  ordinarily  required  in  the  diluted  colloidal  lubri- 
cant. Dr.  Acheson  recommends  a  graphite  content  of  0.35 
per  cent,  for  most  purposes.  That  this  small  amount  has  been 
found  sufficient  is  probably  explained,  by  the  fact  that  colloidal 
lubricants  are  chiefly  used  on  high  class  machinery  with 
reasonably  well  finished  bearing  surfaces. 

Hot  Bearings. — Hot  bearings  may  be  caused  by  excessive 
stresses  or  vibrations,  by  the  accidental  entrance  of  gritty  im- 
purities, by  a  shortage  of  lubricant,  etc.,  etc.  Whatever  the 
cause  may  be  the  oil  film  becomes  entirely  displaced  from  a  small 
portion  of  the  bearing  surface,  a  "dry"  spot  is  formed,  the  sur- 
faces enter  into  intimate  metallic  contact,  the  local  temperature 
rises  rapidly,  the  bearing  seizes,  and  if  it  is  lined  with  white  metal, 
the  latter  may  melt  and  flow  out.  Under  such  conditions,  when 
a  bearing  gives  warning  by  heating,  the  usual  procedure  is  to 
resort  to  the  use  of  a  fixed  oil,  like  castor  or  rape  oil,  or  to  a  vis- 
cous mineral  oil,  like  steam  cylinder  oil;  the  effect  of  using  such 
oils  is  to  produce  a  better  film,  which  separates  the  metallic 
surfaces  and  reduces  the  temperature. 

When  the  surfaces  have  commenced  seriously  to  abrade  one 
another,  oils  may  prove  of  no  avail  and  solid  lubricants  must  be 
used,  such  as  graphite.  The  graphite  particles  by  coating  and 
impregnating  the  surfaces  make  it  difficult  for  the  metallic  sur- 
faces to  seize  and  if  slight  abrasion  takes  place  in  certain  places, 
the  graphite  may  often  succeed  in  repairing  the  damage  and 
make  it  possible  for  the  normal  lubricant  again  to  take  care  of 
the  condition. 

Flowers  of  sulphur  and  white  lead  are  often  used  to  cure  hot 


142  PRACTICE  OF  LUBRICATION 

bearings;  they  act  not  so  much  as  lubricants  but  rather  as  mild 
abrasives;  they  grind  away  the  rough  spots  and  produce  a 
smooth  surface. 

Much  more  drastic  remedies,  such  as  salt,  brick  dust,  and 
grindstone  dust  have  been  successfully  employed  in  very  serious 
cases  of  large  hot  bearings;  their  function  is  to  grind  away 
quickly  the  rough  parts  which  have  commenced  to  seize.  They 
may  be  applied  mixed  with  thick  steam  cylinder  oils  or  castor 
oil,  in  order  to  produce  a  thick  film.  The  oil  should  be  applied 
liberally  in  order  to  clean  away  the  gritty  powder  after  it  has 
done  its  duty. 

In  bearings  which  are  inclined  to  run  hot,  it  is  good  practice 
occasionally  to  apply  a  small  amount  -of  graphite  to  produce  a 
graphitized  surface,  or  to  mix  colloidal  graphite  with  the  normal 
lubricant,  so  as  continuously  to  make  up  the  wear  on  the  graphite 
coating.  In  overloaded  worm  gears,  lor  example,  which  are 
continuously  inclined  to  seize,  it  is  good  practice  to  mix  a  small 
amount  of  flowers  of  sulphur  or  fine  graphite  with  the  oil;  they 
serve  to  prevent  seizure  and  the  wear  becomes  more  uniform. 

METHODS  OF  APPLICATION  AND  USE 

Solid  lubricants  may  be  applied  in  three  different  ways : 

'  (a)  Dry  Application. 

(6)  Mixed  with  Semi-solid  Lubricants. 

(c)  Mixed  with  Liquid  Lubricants. 

Dry  Application. — Solid  lubricants  are  applied  dry  in  cases 
where  for  special  reasons  it  is  inadvisable  or  impossible  to  use 
an  ordinary  liquid  or  semi-solid  lubricant.  The  finely  powdered 
solid  lubricant  is  put  into  a  linen  bag  and  the  bag  is  pounced  or 
struck  against  the  parts  requiring  lubrication;  or  a  syringe  like 
that  used  for  applying  insect  powder  may  be  employed  to  inject 
a  cloud  of  lubricating  powder  into  the  bearings. 

The  following  examples  are  illustrative : 

Lace-making  Machines. — On  certain  reciprocating  parts  pow- 
dered graphite  is  used  in  place  of  oil,  to  avoid  staining  the  fabric. 

Bottle-making  Machines.  Galvanizing  Machines. — Certain 
parts  are  exposed  to  extremely  high  temperatures;  oil  would 
Burn  away  and  leave  a  carbonaceous  residue  which  would  cause 
the  parts  to  stick. 

Chocolate  Machinery. — To  avoid  oil  dropping  into  the  choco- 
late, all  bearings  may  be  lubricated  entirely  by  dry  graphite 
powder.  The  pressures  and  speeds  are  low,  so  that  the  friction 
developed  is  not  too  great  for  comfortable  running. 


BEARINGS  143 

Oil-less  Bearings. — Oil-less  bearings  are  referred  to  page  123. 

For  the  lubrication  of  rubbing  surfaces  made  of  wood,  graphite 
is  very  suitable;  it  is  not  absorbed,  as  is  the  case  with  oil.  The 
graphite  may  also  be  applied  mixed  with  grease,  for  the  sake  of 
convenience  of  handling. 

Steam  Cylinders  and  Valves. — Dry  graphite  in  the  form  of  small 
cylindrical  sticks  has  been  used  in  conjunction  with  oil  for  lubri- 
cating locomotive  valves  and  cylinders,  the  oil  being  supplied  by 
a  separate  lubricator.  The  graphite  sticks  are  placed  in  a  vertical 
tube  and  rest  upon  an  abrasive  wheel,  which  obtains  a  rotative 
or  oscillating  motion  from  some  reciprocating  part  of  the  engine 
(the  valve  rod,  for  example).  In  this  way,  the  abrasive  wheel 
continuously  abrades  the  bottom  graphite  stick  and  the  graphite 
powder  drops  down  a  vertical  passage  direct  into  the  engine. 

Mixture  of  Solid  and  Semi-solid  Lubricants. — The  use  of  a 
solid  lubricant  in  powder  form  is  resorted  to  only  in  special 
circumstances.  When  there  is  no  particular  objection  to  the  use 
of  a  fluid  or  semi-solid  lubricant  and  it  is  desired  to  use  a  solid 
lubricant,  it  is  obviously  desirable  to  mix  the  two  together.  Semi- 
solid  lubricants  are  eminently  suitable  as  carriers  for  solid  lubri- 
cants because  being  non-fluid,  they  prevent  separation  of  the 
graphite,  and,  as  they  are  themselves  gradually  consumed,  they 
automatically  supply  the  solid  lubricant  to  the  parts  which  they 
lubricate. 

The  admixture  of  solid  lubricant  usually  ranges  from  3  per 
cent,  up  to  10  per  cent.,  rarely  exceeding  the  latter  amount. 

Speaking  generally,  semi-solid  lubricants  are  always  improved 
by  the  admixture  of  a  small  amount  of  finely  pulverized  pure 
flake  or  amorphous  graphite.  Exceptions  are  bearings  with 
highly  polished  surfaces  and  small  clearances,  and  high  class 
ball  and  roller  bearings  for  which  colloidal  solid  lubricants  are 
the  only  solid  lubricants  that  can  be  considered. 

Mixture  of  Solid  and  Liquid  Lubricants. — Ordinary  solid 
lubricants  cannot  normally  be  applied  mixed  with  liquid  lubri- 
cants, because,  however  finely  the  solids  may  be  pulverized, 
their  high  specific  gravity  causes  them  to  settle  out  in  the  lubri- 
cators, oil  pipes,  etc.  The  finer  the  particles,  and  the  more 
viscous  the  oil,  the  slower  does  separation  take  place,  so  that 
slight  agitation  may  be  sufficient  to  prevent  separation.  Mix- 
tures of  very  finely  pulverized  solid  lubricants  and  viscous  oils, 
such  as  gear  oil  for  automobile  gear  boxes  may  be  kept  mixed 
by  the  stirring  motion  set  up  by  the  gears. 

Certain  mechanically  operated  graphite-oil  lubricators  for 
steam  engines  are  fitted  with  stirrers  in  the  lubricator  container 


144  PRACTICE  OF  LUBRICATION 

as  well  as  in  the  oil  pipe  leading  from  the  lubricator  to  the 
engine,  to  assist  in  preventing  the  graphite  and  oil  from 
separating. 

This  problem  of  preventing  separation  of  the  solid  lubricant  is 
one  that  is  causing  many  difficulties  and  cannot  be  said  to  have 
been  satisfactorily  solved,  on  account  of  the  mechanical  compli- 
cations which  are  involved. 

Chapman  and  Knowles  have  patented  a  mixture  of  finely 
pulverized  graphite  and  glycerine  for  lubricating  steam  engine 
cylinders.  Before  being  mixed  with  the  glycerine,  the  graphite 
is  impregnated  with  a  sufficient  amount  of  petroleum  or  other 
hydrocarbon  insoluble  in  glycerine,  to  reduce  the  specific  gravity 
of  the  mixture  to  that  of  glycerine-.  As  a  result,  the  "  graphite- 
petroleum"  specks  will  remain  in  suspension  in  the  glycerine, 
and  the  mixture  can  be  pumped  by  a  mechanical  lubricator  and 
supplied  to  the  steam  engine  in  the  ordinary  way. 

Solid  lubricants  can,  of  course,  be  mixed  with  oil  and,  in  the 
form  of  a  more  or  less  liquid  paste,  may  be  applied  by  hand  to 
the  bearings  or  parts  requiring  lubrication.  This  method  is  the 
one  employed  when  "curing"  hot  bearings. 

It  would  appear  that  the  only  really  satisfactory  way  in  which 
a  solid  lubricant  can  be  automatically  applied  mixed  with  a 
liquid  lubricant  is  to  bring  the  solid  lubricant  into  such  a  finely 
divided  state  that  the  particles  become  of  a  size  approximating 
that  of  submicrons.  This  state  of  fineness  cannot  be  obtained 
by  mechanical  means  alone,  but  has  been  attained  by  certain 
processes,  such  as  Dr.  Acheson's  process  already  referred  to. 
Colloidal  solid  lubricants,  when  diluted  with  pure  oil  (oildag, 
oleosol)  or  pure  water  (aquadag,  hydrosol)  do  not  separate  out 
to  any  extent;  they  can  be  diluted  indefinitely  and  can  therefore 
be  applied  to  any  engine  or  machine,  mixed  with  the  dilutent 
which  serves  as  a  carrier. 

Archbutt1  has  made  some  syphoning  tests  with  oildag  and  has 
proved  that  deflocculated  graphite  will  pass  over  with  lubricating 
oil  through  worsted  trimmings  with  but  little  loss  of  its  graphite 
content. 

Many  mechanical  lubricators  employ  a  sight  feed  arrange- 
ment, through  which  the  drops  of  oil  rise  through  a  sight  glass 
filled  with  water;  no  difficulty  is  experienced  with  oil  containing 
colloidal  graphite,  as  the  surface  of  the  oil  is  not  penetrated  by 
the  water.  It  is  different  with  watery  solutions  of  colloidal 
graphite  such  as  aquadag;  they  obviously  cannot  be  passed 
through  water.  Johnston  has  patented  a  lubricator  with  a  sight 
1  ARCHBUTT  and  DEELEY,  "Lubrication  and  Lubricants,"  p.  152. 


BEARINGS  145 

feed  glass  filled  with  kerosene,  through  which  the  drops  of  diluted 
aquadag  sink  down  on  account  of  their  higher  specific  gravity 
as  compared  with  kerosene.  This  arrangement  has  proved 
quite  satisfactory  for  feeding  aquadag  into  the  steam  pipes  of 
engines  using  saturated  steam. 

Drawbacks  to  the  Use  of  Colloidal  Solid  Lubricants. — One 
unsatisfactory  feature  of  colloidal  graphite  solutions  is  their 
black,  "inky"  nature,  which  creates  strong  prejudice  against 
their  use  on  the  part  of  operators  of  engines  or  machinery; 
colloidal  graphite  stains  are  difficult  to  remove  from  the  hands, 
etc.  Colloidal  talc  will  probably  prove  less  objectionable  in 
this  respect  than  colloidal  graphite. 

The  great  drawback  to  all  colloidal  solid  lubricants  is,  however, 
their  susceptibility  to  the  action  of  electrolytes,  as  for  example, 
acids  and  alkalis.  The  presence  of  electrolytes  causes  rapid 
destruction  of  the  colloidal  films  and  flocculation  or  separation 
of  the  solid  lubricant  from  the  liquid  in  which  it  is  diffused.  The 
following  experiments  with  dilute  diffusions  of  oildag  and  aquadag 
in  oil  and  water  respectively,  containing  various  percentages  of 
mineral  acid,  alkali,  fatty  acid,  acetic  acid  and  petroleum  acid 
show  the  tendency  to  flocculation.  The  oil  used  for  the  oildag 
experiments  was  a  neutral  filtered  spindle  oil  to  which  was  added 
the  amount  of  oildag  recommended  by  the  makers,  giving  a 
graphite  content  of  0.35  per  cent,  of  the  blended  oil.  The  results 
are  as  follows : 

Mineral  Acid. — It  was  found  that  even  the  slightest  trace  of 
sulphuric  acid  (H2SO4)  precipitated  the  graphite.  0.1  per  cent, 
of  sulphuric  acid  caused  flocculation  inside  24  hours;  0.005  per 
cent,  caused  complete  flocculation  in  three  days. 

Alkali. — The  results  with  an  alkali  (caustic  soda)  were  very 
similar. 

Dr.  Acheson  himself  has  realized  the  importance  of  the  purity 
of  the  mineral  oils  or  water  used  for  mixing  with  oildag  or  aquadag 
respectively.  He  states: 

"With  deflocculated  graphite  the  very  best  results  will  be  obtained 
when  the  water  or  oil  is  absolutely  pure,  but  commercially  we  may 
perhaps  always  have  a  very  slight  sedimentation  of  the  graphite.  The 
manufacture  of  practically  pure  or  neutral  petroleum  oil  may  be  made 
quite  commercial,  the  presence  of  impurities  in  the  oil  now  placed  on 
the  market  being  almost  solely  due  to  the  failure  of  manufacturers 
properly  to  wash  the  oil.  True,  in  some  instances,  while  thorough 
washing  may  be  performed  with  water,  the  water  itself  is  not  pure, 
which  would  still  cause  impurities  to  be  found  in  the  oil  that  would  be 
capable  of  causing  sedimentation  of  the  graphite,  but  this  residue 
10 


146  PRACTICE  OF  LUBRICATION 

which  is  left  by  natural  waters  when  they  be  of  an  impure  nature,  could 
finally  be  removed  by  a  finishing  wash  with  distilled  water." 

It  is  a  fact  that  most  if  not  all  acid  treated  oils  on  the  market 
are  quite  unsuitable  for  mixing  with  colloidal  lubricants.  The 
most  suitable  oils  are  perhaps  the  so-called  neutral  filtered  oils, 
which  during  the  process  of  refining  have  not  been  in  contact 
with  acids  or  alkalis,  but  are  refined  by  earth  filtration  only. 
Most  neutral  filtered  oils  are  produced  only  with  low  viscosity, 
and  so  the  more  viscous  neutral  lubricating  oils  suitable  for 
blending  with  colloidal  lubricants  may  have  to  be  made  by  mix- 
ing a  neutral  filtered  oil  with  filtered  steam  cylinder  oil. 

Even  with  the  best  of  neutral  filtered  oils,  very  slight  sedi- 
mentation takes  place,  but  it  is  so  slight  as  not  to  be  of  practi- 
cal importance.  The  purity  required  of  the  mineral  oil  is, 
however,  so  essential  that  users  of  colloidal  lubricants  should 
be  warned  not  to  mix  them  with  the  ordinary  grades  of  oils, 
unless  they  have  the  assurance  of  their  suppliers  that  none  of 
the  ingredients  present  contain  acid  or  alkali  or  have  been  acid 
treated. 

Fatty  Acids. — The  flocculating  action  of  fatty  acid  is  not  so 
marked  as  with  mineral  acid.  0.3  per  cent,  of  linseed  oil  fatty 
acid  precipitated  the  graphite  in  four  days;  0.1  per  cent,  of  the 
same  acid  took  two  weeks  to  precipitate  the  graphite  completely. 
Professor  Holde  states  that  "free  organic  acid  need  not  always 
act  as  a  coagulant  even  with  colloidal  graphite;  small  quantities 
may  under  certain  circumstances  act  as  a  stabilizer." 

This  experiment  shows  that,  if  precipitation  of  the  graphite  be 
avoided,  colloidal  lubricants  should  not  be  mixed  with  fatty  oils 
or  compounded  oils  which  contain  a  fair  amount  of  fatty  oil. 

Most  oils  used  for  marine  steam  engines,  locomotives  and  other 
severe  services  are  heavily  compounded  with  vegetable  or  animal 
oil  (from  10  per  cent,  to  30  per  cent.)  and  contain  an  amount  of 
free  fatty  acid,  usually  exceeding  0.5  per  cent. 

Acetic  Acid. — The  action  of  acetic  acid  was  found  to  be  similar 
in  intensity  to  the  action  of  mineral  acid. 

Petroleum  Acids. — Petroleum  acids  (of  a  fairly  volatile  organic 
character)  may  be  produced,  during  use,  in  oils  employed  in 
circulation  systems  in  automobile  engines,  gas  engines,  oilengines, 
and  Diesel  engines. 

In  the  author's  experiments,  petroleum  acid  was  produced  in 
the  oil  by  blowing  air  through  neutral  filtered  spindle  oil  heated 
to  a  high  temperature  (360°F.-400°F.)  to  accelerate  the  oxida- 
tion and  the  formation  of  acid.  To  the  oil  thus  prepared  was 
added  the  prescribed  amount  of  oildag.  The  presence  of  0.1  per 


BEARINGS  147 

cent,  of  petroleum  acid  caused  complete  precipitation  of  the 
graphite  in  five  hours.  When  the  experiment  was  repeated 
with  another  sample  of  oil  similarly  treated,  but  only  slightly 
"  blown,"  containing  0.01  percent,  of  petroleum  acid,  the  flocculat- 
ing action  was  much  less  marked,  but  after  2  weeks  complete 
separation  took  place. 

The  amount  of  petroleum  acid  produced  in  the  oil  during  pro- 
longed use  in  an  automobile  engine  will  not  be  very  great.  0.01 
per  cent,  may  be  considered  an  average  amount,  assuming  that 
the  oil  is  a  neutral  filtered  oil,  and  as  oils  for  automobile  use  are 
fairly  viscous,  there  is  perhaps  not  much  to  fear  from  the  presence 
of  petroleum  acid.  Obviously,  the  more  viscous  the  oil  is  the 
slower  does  the  graphite  separate  out. 

With  splash  oiling  systems  which  do  not  depend  on  circulation 
of  the  oil  by  means  of  a  pump,  there  is  no  danger  in  the  use  of 
colloidal  lubricants,  no  matter  what  kind  of  oil  is  used,  for  if  pre- 
cipitation of  graphite  takes  place,  it  will  merely  accumulate  in 
the  bottom  of  the  engine  and  can  do  no  harm.  But  with  auto- 
mobile engines  employing  an  oil  circulation  system,  highly  puri- 
fied neutral  oils  would  appear  essential  in  connection  with 
colloidal  lubricants,  on  account  of  the  danger  of  choking  up  oil 
pipes,  oil  grooves,  etc. 

Oils  taken  from  enclosed  high  speed  gas  and  Diesel  engines  have 
been  examined,  containing  over  3  per  cent,  of  free  carbon  in  sus- 
pension, which  had  produced  no  ill  effects  on  the  engine.  The 
carbon  had  been  formed  by  carbonization  of  the  lubricating  oil 
inside  the  cylinders,  and  had  worked  its  way  down  into  the 
crank  chamber  and  mixed  with  the  oil;  probably  a  large  amount 
of  this  carbon  was  present  in  colloidal  form.  It  is  a  well-known 
fact  that  black  waste  oil  from  internal  combustion  engines  of  all 
kinds  cannot  be  freed  from  its  carbon  content  by  filtration  and 
that  gravity  separation  in  settling  tanks  may  take  months  to 
accomplish  and  is  rarely  completely  satisfactory. 

The  normal  graphite  content  of  0.35  per  cent,  in  an  oil  blended 
with  colloidal  graphite,  if  separated  out  in  a  engine,  would  be 
considerably  less  than  the  3  per  cent,  of  free  carbon  referred  to 
above,  but  its  nature  being  different,  only  practical  experience 
can  determine  the  actual  risk  incurred,  if  any,  by  the  use  of  such 
"impure"  oils  as  will  cause  precipitation  of  the  graphite. 

Emulsifying  Effect  of  Water. — A  quantity  of  diluted  oildag  was 
mixed  with  an  equal  amount  of  distilled  water  and  shaken  in  a 
reciprocating  bottle-shaking  machine  for  five  minutes  at  room 
temperature.  All  of  the  colloidal  graphite  emulsified  with  the 
water  and  formed  a  tenacious  sludge  which  on  standing  separated 


148  PRACTICE  OF  LUBRICATION 

out  between  the  clear  oil  at  the  top  and  the  clear  water  at  the  bot- 
tom. It  would  appear,  therefore,  that  colloidal  lubricants  should 
not  be  recommended  for  use  in  circulation  oiling  systems,  when 
water  is  likely  to  enter  the  system,  as  is  invariably  the  case  with 
steam  turbines,  enclosed  type,  force-feed  lubricated  steam  engines, 
and  the  like. 

In  many  enclosed  type  internal  combustion  engines  (auto- 
mobile engines,  gas  engines,  etc.)  there  is  no  great  likelihood  of 
water  mixing  with  the  oil  in  service,  and  no  objection  can  be 
raised  to  the  use  of  colloidal  lubricants  from  this  point  of  view. 

When  it  is  desired  to  apply  colloidal  lubricants  temporarily 
to  certain  -bearings,  there  is  no  objection  to  mixing  them  with  the 
lubricant  in  use,  independent  of  the  character  of  the  oil,  because 
the  mixture  is  immediately  introduced,  and  there  is  no  time  for 
the  colloid  to  separate  out  and  cause  trouble. 

If  mixtures  of  " impure"  oil  and  colloidal  lubricants  are  used 
continuously  for  a  period  by  one  of  the  many  comparatively 
slow  feed  oiling  arrangements  (bottle  oiler,  syphon  oiler,  drop  feed 
oiler,  pad  oiler,  etc.)  the  colloid  will  flocculate  and  accumulate, 
the  flow  of  oil  not  being  sufficient  to  wash  it  away.  As  a  result, 
narrow  oil  passages  are  choked,  the  supply  of  lubricant  ceases, 
and  trouble  may  easily  occur. 

Summary. — Finely  pulverized  solid  lubricants  cannot  be  auto- 
matically used  mixed  with  oil  unless  they  are  kept  continuously 
mixed  by  a  special  stirring  mechanism  or  by  the  motion  of  the 
parts  to  be  lubricated. 

With  colloidal  lubricants,  there  is  no  difficulty  in  obtaining  a 
perfect  mixture,  but  it  is  imperative  that  only  very  pure  oils  be 
used  for  making  the  mixture,  unless  the  conditions  of  service  are 
such  that  flocculation  of  the  colloid  is  not  likely  to  lead  to  diffi- 
culties or  trouble  of  a  serious  character. 

OBSERVATIONS  ON  RESULTS  OBTAINED  BY  THE  USE  OF 
SOLID  LUBRICANTS 

Bearings. — There  are  numerous  experiences  which  testify  to 
the  value  of  solid  lubricants,  and  of  graphite  in  particular  for 
use  in  bearings. 

One  British  railway  reports  that  good  results  have  been  ob- 
tained by  using  either  colloidal  graphite  or  flake  graphite  mixed 
with  their  ordinary  loco  engine  oil.  The  graphite  is  not  used  for 
regular  running  (the  compounded  loco  engine  oil  would  cause 
flocculation  of  colloidal  graphite,  and  flake  graphite  cannot  be 
suspended  in  the  oil),  but  only  as  a  temporary  remedy,  whenever 
important  bearings  are  inclined  to  heat. 


BEARINGS  149 

Several  works  report  that  by  continuous  use  of  colloidal  graph- 
ite mixed  with  pure  mineral  oils  they  have  obtained  excellent 
results  on  heavy  duty  bearings  (heavy  pumping  engines,  etc.) 
which  previously  gave  trouble,  even  when  using  oils  heavily  com- 
pounded with  fixed  oil.  Not  only  did  the  bearings  run  cooler, 
but  also  with  an  appreciable  reduction  in  consumption  of  oil  and 
without  flocculation  of  the  graphite. 

Where  no  care  has  been  taken  to  provide  specially  pure  mineral 
oils,  flocculation  has  occurred  and  choking  of  oil  channels,  etc., 
has  resulted. 

Some  bearings  of  high  speed  fans,  which  were  troublesome 
with  oil  alone,  ran  reasonably  cool  when  using  the  same  oil 
mixed  with  colloidal  graphite. 

A  maker  of  dictating  machines  found  that  customers  did  not 
trouble  to  oil  the  motors;  they  tried  oildag  and  found  that,  even 
when  the  motors  received  no  oil  for  several  months  after  the 
initial  application  of  oildag,  no  scoring  occurred,  owing  to  the 
^raphitized  surfaces  produced  in  the  bearings. 

One  maker  of  jaw  crushers  lubricated  the  Pitman  bearing  by  a 
continuous  flow  of  water  mixed  with  some  Hudson's  soap  extract 
and  bicarbonate  of  soda.  The  Pitman  always  groaned  for  about 
15  to  20  minutes  after  starting  up;  after  aquadag  was  used  mixed 
with  the  water  the  groaning  entirely  ceased. 

Saving  in  power  has  been  reported  by  several  firms  resulting 
from  the  admixture  of  colloidal  graphite  with  the  oil  in  use. 

One  important  maker  of  ball  and  roller  bearings  deprecates 
the  use  of  graphite  altogether  for  such  bearings,  reporting  several 
decided  failures  as  a  result  of  using  graphite. 

As  the  chief  object  in  providing  lubrication  for  ball  and  roller 
bearings  is  to  maintain  the  highly  polished  hard  surfaces  in  good 
condition,  and  little  ubricating  properties  are  required,  it  would 
appear  inadvisable  to  use  powdered  or  flaky  solid  ubricants  for 
this  purpose,  as  they  would  probably  not  improve  the  surface  of 
the  balls,  rollers  or  races;  only  colloidal  lubricants  seem  to  have  a 
chance  of  success  for  such  bearings.  The  only  ball  and  roller 
bearings  in  which  the  nature  of  the  lubricant  has  an  influence  on 
the  friction  are  those  in  which  pure  rolling  does  not  take  place 
i.e.,  in  three-  or  four-point  contact  ball  bearings  and  in  roller 
bearings  which  develop  end  thrust;  here  some  rubbing  takes 
place  under  extreme  pressures,  and  if  the  surfaces  are  impregnated 
with  an  exceedingly  fine  solid  lubricant  they  are  likely  to  operate 
with  less  wear  and  friction. 

Some  large  lifts  have  vibrator  wheels  about  5  ft.  in  diameter, 
which  travel  along  a  smooth  shaft  of  8  in.  to  9^  in.  diameter. 


150  PRACTICE  OF  LUBRICATION 

These  wheels  are  bushed  with  cast  iron  and  require  careful  and 
reliable  lubrication.  It  has  been  found  that  by  replacing  ordi- 
nary lubricating  grease  with  a  grease  containing  artificial  amor- 
phous graphite  the  number  of  scored  shafts  and  the  amount  of 
wear  were  materially  reduced. 

The  lubrication  of  worm  and  worm  wheel  reduction  gears  is 
always  difficult;  the  pressure  between  the  teeth  is  very  great; 
even  with  an  abundant  supply  of  oil,  the  friction  consists  of  a 
certain  amount  of  solid  friction  in  addition  to  fluid  friction.  It 
is  therefore  to  be  anticipated  that  the  use  of  graphite  in  connec- 
tion with  the  gear  oil  would  prove  beneficial,  and  the  results  of 
experiments  carried  out  at  the  National  Physical  Laboratory 
with  oildag  and  flake  graphite  on  Lanchesters  worm  gear  testing 
machine  show  this  to  be  the  case.  These  experiments  show  that 
the  addition  of  oildag  to  a  mineral  oil  of  relatively  low  oiliness 
improves  the  gear  efficiency,  so  that  the  results  are  equal  to  those 
obtained  by  animal  or  vegetable  oils. 

Fine  flake  graphite  (Foliac  No.  100)  also  improved  the  effi- 
ciency with  most  of  the  mineral  oils  tested,  and  where  an  improve- 
ment was  recorded  it  was  greater  than  with  oildag.  The  results 
appear,  however,  to  be  less  consistent  and  there  was  distinct 
evidence  of  greater  wear  than  with  oildag. 

When  the  temperature  of  the  oil  is  increased,  a  critical  point  is 
reached  at  which  the  gear  efficiency  rapidly  decreases.  The  effect 
of  adding  oildag  or  flake  graphite  was  in  every  case  to  raise  the 
critical  temperature  about  18°C.  so  that  an  increased  margin  of 
safety  in  operation  was  thus  obtained;  this  happened  even  if  the 
addition  of  solid  lubricant  did  not  increase  the  gear  efficiency  at 
lower  temperatures. 

Steam  Cylinders  and  Valves. — In  many  steam  plants  great 
economies  could  be  effected  if  the  exhaust  steam  could  be  utilized 
for  heating  or  drying  purposes,  for  washing  or  cooking,  or  if 
the  condensed  steam  could  be  used  as  hot  feed  water.  One 
reason  why  this  is  not  done  more  often  is  the  presence  of  cylinder 
oil  in  the  exhaust  steam.  The  oil  can  be  entirely  eliminated  from 
the  condensed  steam  by  electrical  or  chemical  means,  but  not 
from  the  exhaust  steam  itself  before  condensation,  although  good 
oil  separators  may  take  out  as  much  as  99  per  cent,  if  the  cylinder 
oil  is  pure  mineral  in  character,  i.e.,  not  compounded  with  fatty 
oil,  such  as  tallow  oil. 

An  interesting  paper  was  read  by  Mr.  E.  W.  Johnston  in  1916 
before  the  Birmingham  Association  of  Mechanical  Engineers  in 
which  he  gave  his  experiences  with  the  use  of  colloidal  graphite 
(aquadag  diluted  with  water),  the  graphite  contents  of  the  diluted 
mixture  being  0.35  per  cent. 


.      BEARINGS  151 

When  a  suitable  lubricator  had  been  devised  by  Mr.  Johnston, 
aquadag  was  adopted  as  cylinder  lubricant  in  February,  1912,  on 
a  plant  including  three  50-kilowatt  high-speed  vertical  steam 
dynamos,  two  deep  bore-hole  pumping  engines,  boiler  feed,  cir- 
culating, and  other  steam  pumps  supplied  with  saturated  steam 
at  120-pound  pressure. 

The  following  results  were  quoted  by  Mr.  Johnston  in  his  paper: 

"One  of  the  high-speed  engines,  after  accurate  gauging  of  the  valves 
and  cylinders,  was  put  on  a  six  months'  running  test.  At  the  end  of  this 
period  the  greatest  wear  at  any  point  was  found  not  to  exceed  one- 
thousandth  of  an  inch,  and  it  was  particularly  noticed  that  the  walls 
of  the  high  pressure  cylinder  and  piston  rings  were  in  faultless  condition, 
having  mirror-like  surfaces.  Since  uniformly  satisfactory  results  were 
obtained  also  on  the  pumping  engines  and  other  auxiliaries,  the 
entire  plant  has  been  working  with  aquadag  as  the  sole  cylinder  lubricant 
from  February,  1912,  up  to  the  present  moment.  All  available  con- 
densed steam  is  now  returned  to  the  boilers,  so  that  approximately 
10  per  cent,  only  of  make-up  water  is  added  daily.  The  interiors 
of  the  boilers  are  free  from  grease,  practically  clean  down  to  metal, 
save  where  patches  of  old  scale  still  adhere,  and  entirely  free  from  suspi- 
cion of  " pitting."  Formerly  a  considerable  amount  of  scale  of  very 
tenacious  character  had  to  be  dealt  with,  which  resulted  in  loss  of  effi- 
ciency, extra  labor  and  wear  and  tear  to  the  boiler.  Now,  on  the  other 
hand,  a  feed  water  of  considerably  higher  temperature  and  exceptional 
purity  is  available,  resulting  in  further  considerable  fuel  economy. 
After  almost  five  years'  daily  use,  there  is  found  to  be  no  deposit  through- 
out the  receivers,  ports,  valves  and  cylinders  in  excess  of  the  thin  coat- 
ing formed  in  the  first  few  weeks  of  use,  and  little  if  any  trace  in  the 
exhaust  pipes,  condensers  or  other  tracts  beyond  the  engines." 

Mr.  Johnston  kindly  gave  the  writer  a  piece  of  a  piston  ring 
which  had  seen  9  years  total  wear,  the  last  2%  years  with  aqua- 
dag lubrication.  It  was  arranged  to  take  some  microphotographs 
(Fig.  31)  of  the  surface  in  order  to  examine  the  surface  coating  of 
graphite  more  clearly;  it  may  be  remarked  that  the  graphited 
surface  had  a  mirror-like  polish;  these  photographs  were  pre- 
pared by  Mr.  S.  Whyte,  whose  report  is  quoted  herewith : 

" Photos  A,  B  and  C  are  from  the  same  spot  on  the  polished  face. 

A  is  as  received. 

B  after  removing  the  polished  surface  with  0000  French  emery  paper. 

C  after  etching  with  picric  acid  to  show  the  original  structure  of  the 
cast  iron. 

In  each  case  the  free  graphite  of  the  original  cast  iron  is  seen  appearing 
as  bands.  The  deposited  graphite  from  the  oil  is  fairly  evenly  dis- 
tributed, and  is  exceptionally  dense  in  the  softer  matrix  of  the  eutectic, 
i.e.,  in  the  pearlite  areas.  The  cementite  or  iron  carbide  areas  of  the 


152 


PRACTICE  OF  LUBRICATION 


eutectic  are  very  hard,  and  are  seen  standing  in  relief.     The  original 
cast  iron  contains  patches  of  this  eutectic  (which  is  made  up  of  pearlite 


FIG.  31E. 


FIG.  31F. 


and  iron  carbide  bands)  which,  of  course,  is  the  principal  constituent  of  a 
white  cast  iron;  graphite  plates  and  pearlite  areas  being  the  principal 


BEARINGS  153 

constituents  of  a  gray  cast  iron.  Pearlite  itself  is  made  up  of  alternate 
hands  of  pure  iron  and  iron  carbide. 

In  microphotograph  B  till  that  is  seen  is  the  graphite  plates  of  the 
original  cast  iron,  and  here  and  there  among  the  eutectic  area,  specks  .of 
the  deposited  graphite  which  had  penetrated  about  two  ten-thousandths 
of  an  inch,  and  were  not  removed  by  the  polishing. 

Microphotograph  C  shows  the  pearlite  area  (banded  structure, 
and  also  the  eutectic  areas  faintly  outlined.  This  structure  is,  of  course, 
brought  out  by  etching. 

Enclosed  also  are  three  microphotographs  D,  E  and  F,  from  another 
field.  The  focus  is  bad  as,  with  the  curved  surface,  it  is  impossible 
to  get  a  flat  field.  The  same  order  of  things  prevail  but  the  deposited 
graphite  here  is  more  evenly  distributed,  as  the  working  pressures 
appear  to  have  been  higher  on  this  surface  and  the  cast-iron  itself  is 
deformed  to  a  considerable  extent.  The  softer  portions  of  the  iron 
on  the  surface  have  actually  "flowed"  as  can  be  seen  by  the  graphite 
plates  being  partially  covered  over — see  microphotograph  D. 

Light  polishing  on  0000  French  emery  removed  the  deposited  graphite, 
but  did  not  remove  the  surface  layer  of  deformed  iron  which  had  been 
forced  partially  over  the  graphite  plates — see  microphotograph  E. 
This  is  confirmed  by  microphotograph  F  showing  the  broken  up  struc- 
ture of  the  cast-iron  underneath  when  etched  with  acid." 

The  photomicrographs  show  that  the  minute  depressions  or  pores 
in  the  cast-iron  have  been  filled  up  with  graphite  and  that  the  graphite 
coating  is  essentially  a  surface  coating,  although  slight  penetration  of 
graphite  was  observed  in  a  small  soft  area  of  the  surface  (B). 

It  is  reasonable  to  assume  that  Aquadag  can  be  used  on  larger  vertical 
engines  than  those  referred  to  by  Mr.  Johnston,  as  it  is  fairly  eas}* 
to  lubricate  vertical  steam  engines.  The  lubrication  of  horizontal 
engines  is  more  difficult,  and  no  experiments  appear  to  have  been  made 
with  Aquadag  on  such  engines. 

It  would  be  interesting  to  know  how  far  aquadag  or  some  other 
aqueous  colloidal  lubricant  can  be  used  in  connection  with  steam  motor 
vehicles  and  the  like  where  it  is  desired  to  use  condensers  for  the  exhaust 
steam;  its  use  would  make  oil  separators  unnecessary  and  reduce  scale 
formation  in  the  boilers.  The  use  of  aqueous  colloidal  lubricants  is 
probably  limited  to  engines  employing  saturated  steam  and  engines 
of  small  power;  it  must  be  kept  in  mind  that  if  it  were  not  for  the  water 
film  produced  by  steam  condensation  in  the  cylinder,  the  friction  would 
be  very  high  indeed.  In  engines  employing  superheated  steam,  there 
is  little  or  no  condensation  in  the  cylinders  and  it  becomes  necessary  to 
provide  a  lubricating  film  in  order  to  avoid  excessive  friction  and  wear. 

Many  experiments  have  been  made  with  graphite  and  oil  for  the 
internal  lubrication  of  steam  engines  employing  superheated  steam. 
Pure,  fine  flake  graphite  may  be  used,  or  colloidal  graphite  may  be 
mixed  with  the  cylinder  oil,  which  should  preferably  be  a  pure  mineral 
oil,  not  compounded  with  fatty  oil,  as  is  the  case  with  most  good  quality 
steam  cylinder  oils.  The  results  of  graphite  employed  in  this  way  have 
in  many  cases  been  very  satisfactory;  appreciable  reductions  in  con- 


154  PRACTICE  OF  LUBRICATION 

sumption  of  oil  have  been  recorded,  also  less  wear  of  internal  moving 
parts.  Alongside  these  results  there  are  also  a  great  many  failures,' 
although  no  failures  have  been  reported  with  colloidal  graphite.  The 
failures  with  flake  graphite  have  been  due  to  excessive  and  injudicious 
use  of  the  graphite,  or  to  the  use  of  coarse  or  impure  graphite,  or  to 
breakdown  of  the  complicated  lubricators  required  to  keep  the  graphite- 
oil  mixture  well  stirred. 

Under  superheat  conditions  the  surfaces  are  more  difficult  to 
lubricate  than  with  saturated  steam,  and  the  necessity  for  not  over-  * 
feeding  with  graphite  will  be  readily  understood.  Excess  graphite 
accumulates  behind  the  piston  rings  and  in  the  metallic  packing,  and  will 
in  time  make  the  rings  inflexible  in  their  grooves,  resulting  in  scoring 
of  the  surfaces,  leakage  of  steam  past  pistons  and  piston  rods,  etc.,  etc. 
Great  care  must  be  exercised  in  the  use  of  flake  graphite  for  superheated 
steam  conditions,  and  only  the  purest  graphite  must  be  used,  in  order 
to  avoid  excessive  wear  of  pistons,  piston  rings,  cylinders,  piston  rods, 
metallic  packings,  etc. 

Graphite  has  been  used  .by  many  marine  engineers  for  lubricating 
large,  unbalanced  "D"  type  slide  valves.  Cast  iron  being  more  or  less 
porous  is  a  material  particularly  likely  to  benefit  from  the  use  of 
graphite:  when  the  pores  are  filled  and  a  graphite  coating  is  produced 
it  will  be  found  that  an  exceedingly  small  amount  of  graphite  is  required 
to  maintain  the  surfaces  in  good  condition.  Impregnation  of  such 
surfaces  with  graphite  reduces  the  tendency  to  abrasion  and  makes  it 
easier  for  the  cylinder  oil  to  maintain  efficient  lubrication. 

When  a  mixture  of  flake  graphite  and  cylinder  oil  is  used  for  the 
internal  lubrication  of  steam  engines,  the  graphite  will  in  time  find  its 
way  out  with  the  exhaust  steam ;  it  is  easily  separated  from  the  steam  and 
deposited  in  the  oil  separator  or  hot  well.  Flake  graphite  will  adhere  to 
the  baffles  in  the  separator,  and  accumulations  should  be  removed  at 
suitable  intervals. 

In  all  cases  where  the  use  of  graphite  has  brought  about  a  reduction 
in  consumption  of  steam  cylinder  oil,  it  has  also  reduced  the  quantity 
of  oil  reaching  the  boilers,  and  therefore  reduced  the  possibility  of  boiler 
troubles  from  this  source. 

Internal  Combustion  Engines. — The  use  of  solid  lubricants  for  the 
internal  lubrication  of  internal  combustion  engines  has  been  the  subject 
of  much  controversy,  and  various  opinions  have  been  expressed  re- 
garding such  features  as  preignition,  carbon  formation,  sooting  of 
sparking  plugs,  ease  of  starting,  oil  consumption,  and  reduction  in 
friction. 

Preignition  may  be  due  to  accumulation  of  carbon  deposits,  but 
the  cause  of  preignition  appears  to  be  not  so  much  the  carbon  itself  as 
the  earthy  and  other  impurities  (road  dust,  lime,  iron  oxides,  etc.)  which 
may  be  present  in  the  deposit.  Artificial  graphite  whether  in  the  amor- 
phous or  colloidal  form  seems  here  to  possess  advantages  over  most 
natural  graphite,  as  the  presence  of  minute  earthy  impurities  is  more 
easily  avoided  in  artificial  graphite.  As  compared  with  the  use  of  oil 


BEARINGS  155 

alone,  the  tendency  to  preignition  may  be  said  to  be  increased,  more 
or  less,  according  to  the  purity  of  the  graphite. 

Carbon  Formation  and  Sooting  of  Plugs. — Contradictory  reports 
are  received  with  reference  to  this  point.  In  small  engines,  such  as 
motor  cycles,  no  difficulty  is  experienced;  some  records  even  report  less 
sooting  of  plugs  when  using  colloidal  graphite,  but  that  may  perhaps 
be  explained  by  a  more  economical  use  of  the  oil  when  using  graphite. 

The  colloidal  graphite  is  not  consumed  in  the  combustion  space 
but  in  the  form  of  an  exceedingly  fine  dust  spreads  and  adheres  to 
the  walls  of  the  combustion  chamber  and  the  sparking  plugs. 
The  greater  the  consumption  of  oil,  the  more  graphite  is  deposited. 

The  formation  of  oil-carbon  depends  on  the  amount  of  oil 
burnt  inside  the  cylinders  and  on  the  nature  of  the  oil;  some  oils 
produce  more  carbon  than  others,  but  the  amount  of  oil  carbon 
produced  will  normally  never  exceed  0.02  per  cent,  of  the  oil  used. 
Although  hydrocarbon  oils  contain  over  80  per  cent,  of  carbon, 
most  of  the  oil  is  vaporized  and  decomposed  into  other  hydro- 
carbons, with  the  result  that  the  actual  amount  of  oil-carbon 
formed  is  a  very  small  percentage  of  the  amount  of  oil  consumed. 

When  mixing  colloidal  graphite  with  oil  to  give  a  graphite  con- 
tent of,  say,  0.35  per  cent,  in  the  mixture,  it  must  be  remembered 
that  this  graphite  is  not  consumed,  and  unless  a  large  percentage 
of  the  graphite  is  swept  out  by  the  exhaust  gases  or  a  very  large 
reduction  in  oil  consumption  takes  place,  the  formation  of  carbon 
may  easily  be  greater  than  with  oil  alone. 

P^ase  of  Starting. — Opinions  appear  to  be  unanimous  that  when 
graphite  is  used,  engines  (motor  cycles,  automobile  engines,  gas 
engines,  etc.)  start  more  easily  and  with  greater  freedom.  The 
following  contribution  to  " Motor  Cycling"  for  January  23d, 
1917,  may  be  quoted: 

"  I  found  when  using  oildag  that  carbonization  was  markedly  reduced, 
even  under  the  very  heavy  lubrication  that  I  give  my  engine  as  a  rule. 
Engine  'freeness'  (allowing  for  the  inherent  freeness  of  the  engine)  is 
marked.  The  pressure  of  either  valve  spring  acting  on  the  engine 
via  the  tappet  and  cam  was  sufficient  to  rotate  the  back  wheel  of  my 
T.  T.  single  to  the  point  of  rest  of  the  valve  spring,  so  you  can  imagine 
there  was  not  much  friction  in  that  engine.  The  cylinder  walls  took 
on  a  very  high  mirror-like  polish.  I  found  no  concretion  behind 
the  piston  rings,  and  what  carbon  deposit  there  was  in  the  cylinder  head 
and  on  the  piston  top  was  soft  and  easily  removed.  The  effect  of  the 
graphite  on  the  valve  stems,  particularly  such  a  hot-working  stem  as 
that  of  the  exhaust  valve,  was  wonderful.  The  graphite  was  able 
to  resist  the  heat,  and  gave  the  valve  stems  a  similar  'mirror'  surface 
to  that  of  the  cylinder.  I  further  used  it  as  a  general  lubricant  for 
the  cycle  details.  Carburetor  slides  polished  and  lubricated  with 


156  PRACTICE  OF  LUBRICATION 

oildag  worked  very  smoothly  and  with  a  minimum  of  air  leakages. 
It  was  also  useful  as  a  dressing  for  screw  threads  liable  to  bind  or  stick, 
and  on  valve  caps  and  plug  threads;  it  made  a  good  but  easily  broken 
joint." 

Oil  Consumption. — Saving  in  oil  consumption,  made  possible 
by  the  use  of  graphite,  is  due  to  the  smoother  surfaces  of  pistons 
and  cylinders  and  the  more  uniform  and  slightly  smaller  clearance 
space  between  them.  Better  compressions  are  also  obtained  due 
to  less  leakage  past  the  piston.  When  the  initial  oil  consumption 
is  large,  as  with  aircraft  engines,  the  saving  is  apt  to  be  overlooked; 
but  with  small  engines  and  where  adjustable  mechanical  lubrica- 
tors are  employed,  the  saving  obtained  may  be  quite  considerable. 

Reduction  in  Friction. — Speaking  generally,  half  the  friction  in 
an  internal  combustion  engine  is  piston  friction;  'the  lubricating 
oil  film  is  probably  never  complete  and  so  a  certain  amount  of 
metallic  contact  (solid  friction)  invariably  takes  place.  Porous 
cast-iron  surfaces  are  easily  filled  and  coated  by  graphite  and  an 
appreciable  reduction  in  friction  may  be  anticipated  when  the 
necessary  care  is  taken  in  the  judicious  use  of  the  right  kind  of 
graphite. 

In  the  United  States  colloidal  graphite  appears  to  be  exten- 
sively used  for  the  initial  " running  in"  of  automobile  engines; 
it  is  said  to  save  considerable  time  in  producing  a  good  surface 
and  gives  the  engines  a  good  internal  "skin"  before  leaving  the 
builders'  works. 

Ropes,  Chains  and  Gears. — Various  greases  are  usually  em- 
ployed for  the  lubrication  and  preservation  of  ropes,  chains 
and  gears,  and,  as  already  mentioned,  the  admixture  of  a 
small  amount  of  good  quality  finely  divided  graphite  is  beneficial. 
Messrs.  Hans  Renold,  Ltd.,  find  that  with  intermittently  lubri- 
cated chain  drives,  graphite  grease  containing  artificial  amor- 
phous graphite  is  very  suitable.  When  the  chain  has  been  soaked 
in  the  hot  liquid  grease  it  will  work  without  further  lubrication 
for  a  long  period,  sometimes  for  several  months,  whereas  with  thin 
oil  in  use  it  must  be  applied  at  least  once  a  week,  and  then  the 
results  are  not  always  satisfactory,  a  reddish  deposit  (rust)  being 
found  in  the  bearings  of  the  chain.  With  graphite  grease  this 
deposit  does  not  form.  The  same  firm  also  reports  that  the 
clutch  band  in  their  power  clutches,  when  lubricated  by  graphite 
grease,  requires  no  attention  for  long  periods. 

When  chains  or  gears  are  enclosed  in  an  oil  tight  casing,  the 
use  of  an  oil  bath  is  preferable  to  grease;  in  this  case  the  admix- 
ture of  a  small  amount  of  finely  pulverized  graphite  or  colloidal 
graphite  is  also  beneficial.  Messrs.  Hans  Renold,  Ltd.,  report 


BEARINGS 


157 


some  interesting  results  from  the  use  of  diluted  oildag  in  connec- 
tion with  chains,  lubricated  by  an  oil  bath.  Their  figures  are 
as  follows: 

Power  of  motor • 20  H.P. 

Length  of  line-shaft 90  ft. 

No.  of  line-shaft  hangers 10 

No.  of  chain  drives 25 

Total  length  of  chain  drives 275  ft. 

Line-shaft  speed ' 310  r.p.m. 

RATE  AT  WHICH  ELECTRICAL  ENERGY  WAS  CONSUMED  IN  WATTS 

After  105  hr.  run 


Conditions 

up   c  )hl 

run 

Starting 
up  e,  1(1 

After  short 
run 

Line-shaft  hangers  and  chains  lubri- 

cated with  ordinary  oil  

$008 

4,000 

Chain  lubricated  with  oildag  

3,750 

Line-shaft  hangers  lubricated  with 

oildag  

.... 

3500 

Chain  and  hangers  lubricated  with 

oildag  

.... 

4,000 

3,000 

On  further  application  of  oildaf*;  to 

chains  

2,500 

Metal  Cutting  and  Wire  Drawing. — Colloidal  solid  lubricants 
— such  as  aquadag — have  been  used  as  coolants  for  cutting  pur- 
poses. Experiments  seem  to  indicate  that  colloidal  solid  lubri- 
cants are  not  satisfactory  when  used  for  this  purpose  by  themselves. 
They  do  not  flow  to  the  tool  point  if  it  is  greasy,  and  the  tool 
point  therefore  wears ;  when  they  are  mixed  with  ordinary  cutting 
emulsions  or  soap  and  water,  good  results  have  been  obtained,  but 
the  high  first  cost- of  colloidal  lubricants  militates  against  their 
use  for  cutting  purposes;  the  staining  effect  of  the  graphite  on 
the  hands  of  the  operators  is  also  objectionable. 

In  metal  wire-drawing  operations  semi-solid  lubricants  are 
used,  such  as  mixtures  of  olive  soap  and  powdered  talc.  There 
appears  to  be  no  reason  why  a  vegetable  soap  mixed  with  a 
suitable  amount  of  finely  powdered  graphite  should  not  be  capa- 
ble of  rendering  good  service. 

Aquadag  is  used  in  wire-drawing  the  metal  filaments  (Demp- 
sters Patent  No.  17722  of  1911)  used  in  electric  lamps;  the  dies 
require  a  certain  amount  of  lubrication  to  produce  a  satisfactory 
thread,  and  aquadag  is  apparently  the  only  non-oily  lubricant 
which  has  given  satisfaction  for  this  purpose. 


CHAPTER  IX 
r       RING  OILING  BEARINGS 

Ring  oiling  is  largely  employed  on  modern  high-speed  shafting 
bearings,  practically  all  electric  motors  and  electric  generators, 
also  small  steam  turbines.  Main  bearings  in  most  gas  engines, 
Diesel  engines,  and  horizontal  oil  engines,  as  well  as  many  steam 
engines,  employ  the  ring  oiling  system  f  °r  the  crank  shaft  bearings. 

The  advantages  of  ring  oiling  over  the  drop  oiling  system  are 
many,  such  as: 

1.  Better  and  more  uniform  lubrication. 

2.  Greater  oil  economy. 

3.  Greater  factor  of  safety  in  operation. 

4.  Greater  cleanliness. 

5.  Less  attention  required. 

Ring  oiling  is  used  for  small  as  well  as  large  bearings,  but  not 
for  the  very  smallest,  say,  below  2  inches,  running  at  high  speeds, 
as  the  rings  frequently  fail  to  operate  and  it  is  difficult  to  pre- 
vent frothing  and  waste  of  oil. 

The  bearing  housing  (Figs.  34 A  and  345),  forms  an  oil  reservoir 
in  which  the  oil  is  maintained  at  a  certain  level,  preferably  indi- 
dicated  by  an  oil  gauge  which  may  also  serve  for  the  introduction 
of  the  oil. 

On  the  shaft  is  usually  suspended  one  or  two  rings  or  chains 
dipping  into  the  oil ;  when  revolving,  the  rings  carry  oil  to  the  top 
of  the  shaft,  from  which  it  runs  into  the  oil-distributing  groove  on 
the  "on  side"  of  the  journal  and  spreads  over  the  bearing  sur- 
faces. This  groove  extends  to  within  J£  inch  of  the  bearing 
ends  and  is  well  chamfered  to  facilitate  the  oil  wedging  its  way 
into  the  bearing.  If  the  motor  is  reversible,  two  oil-distributing 
grooves  are  obviously  needed,  one  on  each  side.  No  other  oil 
grooves  should  ordinarily  be  made,  as  the  high  surface  speed 
assists  the  oil  materially  in  getting  in  between  the  rubbing 
surfaces. 

When  the  surface  speed  is  low  and  the  bearing  pressure  high, 
oil  grooves  may  be  advantageous,  as  explained  page  115. 

When  speeds  are  low,  or  the  oil  becomes  thick  (cold  mornings) 
oil  rings  may  not  start  readily.  Fig.  32  illustrates  an  oil  ring 
with  notches  filed  on  the  inside,  which  is  said  to  assist  the  ring 

158 


RING  OILING  BEARINGS 


159 


in  starting,  owing  to  the  greater  friction  between  the  ring  and 
the  shaft. 

For  low-speed  bearings,  oil  rings  are  sometimes  replaced  by 
chains,  which  touch  the  shaft  over  a  longer  arc  and  are  therefore 
kept  in  motion  with  greater  certainty  than  plain  rings.  At  high 
speeds  chains  have  the  disadvantage  that  the  links  churn  the  oil, 
which  leads  to  foaming  and  leakage  of  oil  rom  the  bearings. 

When  the  speeds  are  exceptionally  low,  say  a  few  revolutions 
per  minute,  neither  rings  nor  chains  are  satisfactory,  and  oil 
rings  or  collars  fixed  on  the  shaft  are  employed,  whence  the  oil  is 
removed  by  stationary  scrapers  in  the  upper  part  of  the  bearing, 
guiding  the  oil  afterward  into  the  oil-distributing  groove.  Such 
bearings  are  employed  on  the  drying  cylinders  of  paper-making 
machines  and  other  slow  speed  machinery,  but  are  also  occa- 
sionally used  for  moderate  speed  machines.  Oil  rings  are  usually 


Ill 


FIG.  32.— Notched  oil  ring. 


(^    tel 

FIG.  33. — Various  types  of  oil  rings. 


made  twice  the  diameter  of  the  journal,  the  oil  level  being  at 
a  distance  below  the  shaft  about  half  its  diameter. 

One  oil  ring  will  suffice  for  bearings  up  to  8  inches  in  length. 
Two  oil  rings  are  needed  for  bearings  from  8  inches  to  16  inches 
in  length,  and  three  oil  rings  for  larger  bearings. 

As  to  the  shapes  of  oil  rings,  there  are  a  great  many;  some  are 
indicated  in  Fig.  33.  They  should  preferably  be  made  un- 
divided. When  made  in  two  halves  and  jointed,  slight  wear  may 
cause  the  rings  to  operate  irregularly  or  even  refuse  to  revolve. 
Unevenness  at  the  joint  at  high  speed  leads  to  foaming  of  the 
oil  and  oil  spray.  Unevenness  or  roughness  on  the  two  sides  of 
the  oil  ring  will  have  similar  effects.  Rings  which  are  slightly 
oval,  due  to  lack  of  care  during  manufacture,  will  obviously  be 
inclined  to  stick. 

In  large  bearings,  cooling  of  the  oil  by  introducing  a  cold  water 
coil  in  the  reservoir  may  be  found  desirable  or  even  necessary 
under  severe  conditions.  (See  Turbines.) 


160 


PRACTICE  OF  LUBRICATION 


Difficulties  sometimes  occurring  with  ring  oiling  are: 

(a)  Foaming  and  spraying. 

(6)  Leakage,  endways  or  sideways. 

Foaming  and  Spraying.— Traubles  of  this  kind  may  be  due  to 
too  high  revolving  speed  of  the  oil  rings,  or  to  too  low  an  oil 
level  (which  brings  about  quick  speed  of  the  rings  owing  to  the 
smaller  resistance  offered  to  the  movement  of  the  rings  through 
the  oil).  The  oil  is  violently  thrown  away  from  the  rings  form- 
ing oil  spray,  oil  foam  being  formed  by  the  rings  drawing  air 
into  the  oil  where  they  enter  the  oil  well.  Excessive  foaming 
and  oil  spray  always  mean  waste  of  oil,  as  the  finest  oil  spray 


Fig.  34A 


Fig.  34 

Fig.  34C        ,  Fig.  34D 

FIG.  34. — Ring  oiling  bearing. 

finds  its  way  through  the  bearing  ends  or  covers.  Such  loss  of 
oil  may  become  dangerous  by  lowering  the  oil  level  so  much  that 
the  bearings  will  receive  too  little  oil. 

Leakage  through  the  side  of  the  bearing  between  the  top  and 
bottom  parts  can  be  overcome  by  inserting  a  thin  leaden  wire 
which,  when  the  bearing  is  put  together,  is  squeezed  flat  and  forms 
a  seal  (Fig.  34JD).  The  lip  (1)  in  Fig.  345  is  intended  to  prevent 
such  oil  leakage;  also  the  longitudinal  drainage  groove  (2)  in 
Fig.  34C,  which  is  sometimes  found  in  large  bearings,  draining 
the  oil  back  to  the  reservoir  at  its  two  ends. 

The  proper  remedy  is,  however,  to  have  a  type  of  oil  ring  suit- 
able for  the  size  and  speed  of  the  shaft.  The  speed  of  the  oil 
rings  is  governed  by  the  propelling  force  caused  by  oil  adhesion 
between  the  ring  and  the  journal,  where  they  touch  at  the  top, 


RING  OILING  BEARINGS  161 

and  the  retarding  force  caused  by  the  opposition  to  movement 
created  by  .the  speed  of  the  ring  through  the  oil  in  the  well.  It 
will  be  recognized  that  oil  rings  Nos.  2,  3,  4  and  5  will  give  lower 
ring  speeds  (more  slip)  than  oil  ring  No.  1;  whereas  No.  6  will 
usually  give  greater  speed  than  No.  1  owing  to  less  surface  in 
contact  with  the  oil — therefore  less  resistance  with  the  same  pro- 
pelling force.  By  finding  out  from  practical  experiments  which 
type  of  ring  gives  a  suitable  speed,  and  oil  feed,  the  majority  of 
troubles  with  ring  oiling  bearings  may  be  overcome. 

It  is  particularly  important  to  study  this  point  when  outside 
the  bearing  there  is  a  pulley,  which  in  revolving  creates  a  suction, 
tending  to  increase  loss  of  oil  from  the  bearing.  The  oil  when 
leaving  the  ends  of  the  bearing  drops  back  into  the  oil  reservoir 
and  is  thus  kept  in  constant  circulation.  If  the  bearing  is  well 
designed,  there  will  be  very  little  oil  waste  by  leakage  or  oil 
creeping  along  the  shaft.  Sometimes  the  oil  creeps  spirally  along 


1  Oil  King 

2  Oil  Throwers 


FIG.  35. — Simple  oil  thrower, 

the  shaft  and  is  thrown  away  where  it  is  least  desired,  creating 
unsightly  oily  floors,  or  spoiling  fabrics  (cloth  looms,  for  example). 
The  remedy  may  lie  in  lowering  the  oil  level  or  altering  the  type 
of  oil  ring,  but  the  root  of  the  trouble  may  be  wrong  shaping  of 
the  bearing  surfaces.  Fig.  34  A  shows  how  the  edge  must  be 
rounded  off,  which  helps  to  prevent  oil  creeping,  whereas  a  sharp 
edge  does  not  hinder  the  oil  in  passing  along  the  shaft. 

An  excellent  arrangement  is  to  have  a  circumferential  oil  groove 
with  sharp  edges  as  shown  in  Fig.  34A  with  a  drainage  hole-at  the 
bottom;  in  addition,  a  longitudinal  drainage  groove  also  with 
sharp  edges  will  assist  in  preventing  excess  oil  reaching  the  bear- 
ing ends,  as  shown  at  the  right-hand  side  of  Fig.  34A.  Other 
methods  rely  upon  oil  throwers  formed  on  the  shaft  and  suitable 
shapes  of  bearing  housings  at  the  end  to  receive  the  oil  and  convey 
it  to  the  oil  reservoir. 

Fig.  35  shows  the  simplest  form  of  oil  throwers.  This  con- 
n 


162  PRACTICE  OF  LUBRICATION 

struction  with  a  drainage  passage  from  left  to  right  through  a 
centre  wall  in  one  case  caused  the  oil  to  overflow  from  the  left- 
hand  chamber,  owing  to  the  passage  being  almost  choked  with 
dirt  . 

Bearing  Clearance. — A  clearance  of  0.002  in.  +  0.001  in.  per 
inch  of  shaft  diameter  represents  normal  practice  and  will  give  sat- 
isfaction as  long  as  the  deflection  of  the  shaft  due  to  an  overhang- 
ing pulley,  heavy  flywheel,  or  rotor  close  to  the  bearing  does 
not  exceed  this  clearance. 

To  take  care  of  such  shaft  deflection  medium  and  large  size 
bearings  are  frequently  self -aligning,  being  made  with  spherically 
seated  housings. 

Care  of  Ring  Oiling  Bearings. — When  ring  oiling  bearings  are 
well  designed,  with  large  oil  wells  and  employing  good  quality 
oils,  they  will  operate  for  long  periods  without  undue  attention 
or  loss  of  oil.  During  the  first  few  weeks  of  service  the  oil  wells 
of  new  bearings  should  be  emptied  and  recharged  with  fresh  oil 
every  few  days  in  order  to  remove  any  molder's  sand  or  grit 
which  may  still  be  present  in  the  bearing.  Once  the  bearing  is 
clean  and  a  good  "skin"  formed  it  will  be  sufficient  to  empty  the 
wells  every  three  months  and  recharge  them  with  fresh  oil,  or  a 
mixture  of  filtered  and  fresh  oil.  When  the  bearings  are  situated 
in  dusty  surroundings,  more  frequent  changes  of  the  oil  may  be 
desirable,  as  dust  will  find  its  way  into  the  oil,  notwithstanding 
precautions  in  the  way  of  wooden  or  felt  rings  fitted  in  the  bearing 
ends;  of  course  such  rings  do  reduce  the  amount  of  dust  which 
enters.  Where  chemical  fumes  are  present  in  the  air,  which  have  a 
destructive  effect  on  the  oil,  it  must  also  be  changed  frequently. 

When  good  quality  mineral  oil  is  used  it  can  be  filtered  and 
used  over  and  over  again,  so  that  the  oil  consumption  per  year  is 
usually  very  small.  When  oils  with  a  mineral  base,  but  com- 
pounded with  animal  or  vegetable  oils,  are  employed,  they  will 
develop  gumminess  in  the  bearings  and  necessitate  cleaning. 
Such  cleaning  is  unnecessary  when  straight  mineral  oils  are  em- 
ployed ;  cases  have  been  known  where  good  quality  oils  have  been 
in  use  for  years  without  any  real  necessity  for  cleaning  the  bear- 
ings or  the  oil  wells. 

When  a  change  is  made  from  a  compounded  oil  to  a  mineral  oil, 
the  latter  will  loosen  the  accumulations  formed  by  the  old  oil. 
In  such  cases  it  is  advisable  to  renew  the  charge  after  a  few  weeks' 
run;  the  oil  when  withdrawn  will  be  very  dark  in  color,  due  to  the 
deposits  and  perhaps  very  slight  initial  wear  due  to  the  bearing 
surfaces  adapting  themselves  to  the  new  oil,  but  a  fresh  charge 
ought  to  work  clean,  if  the  new  oil  is  of  the  right  quality,  and  the 
bearing  has  been  completely  cleansed. 


CHAPTER  X 
ELECTRIC  GENERATORS  AND  MOTORS 

Satisfactory  bearing  lubrication,  i.e.,  cool  running  and  inappre- 
ciable wear,  is  very  important.  If  wear  takes  place,  the  rotor 
is  lowered,  and  the  magnets  will  then  exert  a  pull  on  the  rotor  in 
a  downward  direction,  which  further  increases  the  bearing  pres- 
sure and  accordingly  the  wear.  Most  bearings  therefore  operate 
with  bearing  pressures  of  50  to  100  Ib.  per  square  inch  and  are 
oil  flooded. 

Ring  oiling  bearings  are  most  frequently  used. 

Ball  bearings  are  also  coming  much  into  use,  particularly  as 
smaller  size  horizontal  bearings  and  as  vertical  bearings,  and  in 
dusty  surroundings,  ^in  which  case  grease  is  often  used  in 
preference  to  oil. 

When  a  new  generator  or  motor  exhibits  a  tendency  to  develop 
heat  in  one  bearing,  the  bearing  should,  of  course,  be  examined. 
If  it  be  found  in  good  condition,  the  cause  of  the  heating  may  be 
found  in  the  thrust  of  the  armature  shaft  against  the  bearing, 
which  may  result  from  one  of  two  conditions.  First,  the  machine 
may  not  be  level  and  the  armature  shaft  may  "dip."  Second, 
the  magnetic  centres  of  the  pole  pieces  and  armature  may  not  be 
in  line;  that  is,  the  pole  pieces  may  hot  be  exactly  centered  in  their 
relation  to  the  magnetic  centre  of  the  armature  axially,  and  as 
the  tendency  of  the  armature  is  to  run  to  the  true  magnetic 
centre,  it  will  automatically  tend  to  move  toward  that  position, 
which  may  cause  the  shaft  collar  to  rub  against  the  bearing  at  one 
end,  and  cause  heating. 

The  unbalanced  magnetic  condition  may  have  been  caused  by 
forcing  the  armature  not  quite  far  enough  or  a  trifle  too  far  on  to 
the  shaft  in  the  factory.  Some  motors  are  furnished  with  slots 
in  the  field  magnet  yoke  through  which  the  field  magnet  cores 
are  bolted  to  the  yoke,  and  the  cores  may  be  shifted  a  trifle  to 
the  right  or  left  to  compensate  for  any  slight  axial  unbalancing 
of  the  magnetic  centre  as  compared  with  that  of  the  armature. 
Moving  the  magnet  cores  Y\  §  of  an  inch  will,  as  a  rule,  be  suffi- 
cient to  give  relief.  If  the  field  magnet  yoke  is  not  slotted,  a  light 
cut  may  be  taken  off  the  shoulder  of  the  shaft,  at  the  end  which 

163 


164 


PRACTICE  OF  LUBRICATION 


rubs   against   the   bearing,   in   order   to   obtain    the   necessary 
clearance. 

Oil  throwing  from  the  bearings  into  the  generator  or  motor  is  a 
troublesome  disease  often  very  difficult  to  cure.  Several  reme- 
dies have  been  mentioned  under  ring  oiling  bearings  but  they  are 
not  always  effective  with  those  types  of  electric  dynamos  which 
create  a  draught.  When  the  generator  is  enclosed  and  the  venti- 
lation led  in  from  below,  this  danger  does  not  exist,  or  at  any 
rate  only  to  a  slight  extent;  but  when  the  generator  is  not  en- 
closed, the  oil  finds  its  way  into  the  ventilating  ducts,  tending  to 
choke  them  with  dirt  and  dust,  which  adhere  to  the  oil.  The 


FIG.  36. 


FIG.   37. 
FIGS.  3G-38. — Oil  throwers. 


oil  also  gets  on  to  the  commutator  or  slip  rings  and  causes 
sparking. 

In  Figs.  36,  37  and  38  are  illustrated  some  more  elaborate 
methods  adopted  to  prevent  oil  throwing.  Fig.  37  shows  a 
series  of  thin  copper  plates,  which  only  lightly  touch  the  shaft 
and  thus  create  an  effective  labyrinth  seal;  but  they  are  inclined 
to  cause  wear  of  the  shaft,  small  gritty  particles  embedding  them- 
selves in  the  soft  copper  surfaces.  Certain  information  on  this 
subject  is  also  given  under  " Turbines." 

It  is  said,  and  it  sounds  quite  feasible,  that  compounded  oils 
do  more  damage  when  getting  on  to  the  windings  than  straight 
mineral  oils,  as  they  absorb  moisture  and  thus  reduce  the  insula- 
tion resistance  of  the  armature  more  than  straight  mineral  oils, 
which  are  not  hygroscopic. 

Commutator  Lubrication. — Lamp  oil  (kerosene)  used  very 
sparingly  is  probably  the  best  oil  to  keep  the  commutators  clean 
and  well  lubricated.  It  also  softens  the  mica  and  thus  causes 
it  to  wear  down  so  that  it  does  not  stand  out  beyond  the  bars. 


ELECTRIC  GENERATORS  AND  MOTORS  165 

DYNAMO  OILS 

Three  grades  of  dynamo  oils  will  take  care  of  most  require- 
ments; they  are  all  pure  minerals  oils,  namely,  Bearing  oils  Nos. 
2,  4,  and  5  (see  page  128).  The  oil  is  somewhat  exposed  to 
oxidation  during  its  continuous  circulation  in  the  bearings,  but 
as  long  as  the  bearing  temperatures  do  not  exceed,  say.  120°F. 
there  is  no  need  to  have  specially  prepared  dynamo  oils;  where 
the  oil  exceed  temperature  120°F.,  circulation  oils  of  the  corre- 
sponding viscosities  should  be  preferred  to  ordinary  bearing  oils. 

A  rough  guide  for  selecting  the  correct  viscosity  of  dynamo  oil 
is  given  in  the  following  chart : 

LUBRICATION  CHART  NO.  2 
FOR  ELECTRIC  GENERATORS  AND  MOTORS 

Bearing  Oil  No.  2  or  Circulation  Oil  No.  1. — For  small  elec- 
tric generators  or  motors  up  to  50  H.P.  and  up  to  100  H.P.  when 
there  is  no  excessive  belt  pull  on  the  shaft  close  to  the  bearing. 

Bearing  Oil  No.  4.  or  Circulation  Oil  No.  2. — For  larger  electric 
generators  and  motors  under  normal  operating  conditions,  and 
for  motors  below  100  H.P.  with  excessive  bearing  pressures. 

Bearing  Oil  No.  5  or  Circulation  Oil  No.  3. — For  generators  or 
motors  above  100  H.P.  operating  with  excessive  bearing  pressures. 

Ball  bearing  grease  is  employed  only  for  smaller  motors,  operat- 
ing in  dusty  surroundings  or  in  hot  and  moist  climates. 


CHAPTER  XI 
PLAIN  THRUST  BEARINGS 

Horizontal  thrust  bearings  are  designed  to  take  up  axial  thrusts 
of  revolving  parts,  as  for  example  in  horizontal  centrifugal  pumps 
or  turbines  or  the  propeller  shafts  in  marine  steam  engines. 

Vertical  thrust  bearings  are  employed  to  carry  the  weight  of 
revolving  parts,  as  in  vertical  water  turbines  or  centrifugal 
pumps,  vertical  electric  generators  or  motors. 


FIG.  39. — Ring  oiled  thrust  bearing. 

Collars  on  the  shaft  transmit  the  pressure  to  stationary  collars, 
various  means  being  employed  to  introduce  an  oil  film  between  the 
rubbing  surfaces,  as  described  under  ''Turbines"  and  "Marine 
Steam  Engines."  Fig.  39  illustrates  a  method  of  oiling  the  thrust 
bearing  in  high-speed  pumps  by  means  of  an  oil  ring  (1) ;  the  oil  is 
thrown  off  the  collar  (2)  against  the  oil  catcher  (3)  whence  it 
runs  into  the  oil  cup  (4)  and  reaches  the  hollow  shaft,  finally 
returning  to  the  oil  well.  The  lower  part  of  the  bearing  is 

166 


PLAIN  THRUST  BEARINGS 


167 


water  cooled.  Fig.  40  illustrates  an  unsatisfactory  method,  as 
the  large  oil  disc  (2)  causes  foaming  and  creates  heat. 

Fig.  41  illustrates  an  ingenious  method  of  providing  oil  circula- 
tion in  a  vertical  thrust  bearing  supporting  a  shaft  revolving  at 
1,500  r.p.m.  upon  which  is  fitted  an  electric  motor  driving  a  cen- 
trifugal deep  well  pump  at  the  lower  end  of  the  shaft. 

The  shallow  spiral  grooves  on  the  part  (1)  lift  the  oil  into  the 
oil  chamber  (2);  the  oil  pressure  created  here  drives  the  oil 
through  the  oil  drillings  in  the  shaft;  the  oil  after  doing  its  work 
reaches  the  oil  return  channel  (3)  and  the  oil  well  (7)  which  is  so 


FIG.  40. 


FIG.  41. — Vertical  thrust  bearing  automatic  oil 
circulation. 


arranged  that  the  oil  cannot  overflow  down  the  shaft.  The  drain 
plug  (4)  is  removed  when  it  is  desired  to  empty  the  bearing,  and 
when  the  bearing  is  being  filled  through  the  filling  plug  (5),  the 
overflow  plug  (6)  is  removed  so  as  to  ensure  a  correct  oil  level. 
When  thrust  bearings  have  only  one  collar  or  one  rubbing  surface, 
they  are  called  step  bearings  or  pivot  bearings. 

Fig.  42  illustrates  the  simplest  form  of  step  bearing;  the  revolv- 
ing shaft  rests  on  three  washers ;  the  top  washer  may  be  arranged 
to  revolve  always  with  the  shaft,  so  as  to  save  wear  of  the  shaft 
itself.  With  low  bearing  pressure  only  one  washer  is  needed; 
the  higher  the  pressure  the  more  washers  are  required.  When 


168 


PRACTICE  OF  LUBRICATION 


one  washer  begins  to  heat  and  seize,  it  stops  revolving  and  one  of 
the  cooler  washers  commences  to  revolve,  so  that  they  more  or 
less  divide  the  work  between  them,  only  one  washer  acting  at  a 
time. 

The  washers  should  always  have  shallow  radial  oil  grooves 
cut  in  their  rubbing  faces,  the  grooves  stopping  slightly  short  of  the 
edges,  and  the  trailing  edges  of  the  grooves  should  be  well  rounded 
to  facilitate  the  entrance  of  oil  between  the  surfaces. 

The  oil  enters  the  central  hole,  rises  to  the  top,  due  to  cen- 
trifugal action,  and  returns  through 
the  drain  hole.  When  such  bear- 
ings get  uncomfortably  warm,  a 
remedy  is  to  increase  the  flow  of  oil 
by  means  of  a  pump  which  forces 
the  oil  in  under  pressure;  the  oil 


6 


FIG.  42. — Step  bearing. 


FIG.  43. — Water  turbine  bearing. 


returns  from  the  top  through  a  pipe  into  an  oil  reservoir,  whence 
the  pump  draws  its  supply.  In  this  way  a  greater  radiating 
surface  is  obtained  and  the  bearing  will  run  cooler. 

Vertical  water  turbines  make  use  of  bearings  as  illustrated  in 
Figs.  43, 44  and  45.  In  Fig.  43  the  weight  of  the  turbine  is  taken 
by  a  stationary  vertical  shaft  (1)  which  has  an  oil  reservoir  (2) 
at  the  top  with  a  bronze  washer  (3).  The  hollow  revolving 
shaft  (4)  carries  the  weight  of  the  revolving  parts  and  transmits 
the  pressure  through  the  hardened  steel  part  (5)  to  the  washer 
(3).  Oil  is  fed  through  the  top  from  a  sight-feed  drop  oiler  (6). 
The  overflow  oil  runs  down  into  the  guide  bearing  (7),  which  is 


PLAIN  THRUST  BEARINGS 


169 


FIG.  45. 
FIGS.  44,  45.— Water  turbine  bearings. 


170 


PRACTICE  OF  LUBRICATION 


under  water;  at  the  lower  end  there  is  a  gland  packing  to  prevent 
entrance  of  water  into  the  hollow  shaft,  but  as  some  water  gen- 
erally gets  in,  compounded  oils,  such  as  Marine  Engine  Oil  No.  1 
or  No.  2  (see  page  258)  should  be  used,  which  will  emulsify  with 
the  water  and  maintain  efficient  lubrication. 

In  Fig.  44  the  shaft  (1)  and  washer  (2)  revolve;  the  stationary 
washer  (3)  receives  the  full  pressure  and  transmits  it  through  the 
stationary  shaft  (4)  and  cover  piece  (5)  to  the  casing  (6).  The 
oil  circulates  continuously  through  the  oil  grooves,  which  extend 
right  to  the  edge.  It  will  be  noticed  that  the  bearing  surface 
in  this  design  is  very  small;  the  bearing  is  very  compact,  so  that 
a  rich  viscous  oil,  as  Marine  Engine  Oil  No.  1  must  be  used. 

In  Fig.  45  the  bearing  surface  is  much  bigger,  also  the  radiating 
surface  is  greater,  which  gives  cooler  running;  ordinarily  a  slow 


FIG.  46. — Michell  thrust  pads. 

oil  feed  from  a  sight  feed  drop  oiler  suffices,  but  where  high 
pressure  exists  and  the  heat  developed  is  great,  an  oil  circulation 
system  may  be  employed. 

The  oil  to  use  in  such  bearings  as  Figs.  40,  41  and  45  may  well 
be  Circulation  oil  No.  1  or  2,  as  the  bearing  pressure  is  low,  and 
the  revolutions  are  usually  high,  say  above  100  r.p.m. 

A  special  type  of  step  bearing  is  employed  in  the  Curtiss  vertical 
turbines,  as  described  page  230. 

By  far  the  most  satisfactory  and  reliable  type  of  thrust  bearing 
for  heavy  pressures,  whether  the  speeds  are  high  or  low,  is  the 
Michell  single  collar  thrust  bearing.  The  collar  or  footstep  rests 
upon  a  fixed  bearing  surface,  which  is  divided  into  a  number  of 
segmental  pads,  each  pivoted  so  that  it  is  free  to  rock  and  take 
up  any  inclination  to  the  moving  surface,  which  the  conditions 
of  speed,  pressure,  and  viscosity  of  the  oil  may  demand.  Fig.  46 
shows  two  methods  of  supporting  the  pads,  viz.,  pivoting  along  a 
line  and  on  a  point,  the  pivoting  line  or  point  being  placed  a 


PLAIN  THRUST  BEARINGS  171 


FIG.  47. 


172 


PRACTICE  OF  LUBRICATION 


little,  behind  the  centre  of  each  pad;  experience  shows  this  to  be 
important  to  give  a  perfect  film  and  therefore  minimum  friction. 
As  the  collar  (1)  moves  over  the  pad  (2)  a  wedge-shaped  oil  film  is 
established;  the  oil  is  continuously  drawn  in  at  the  leading  edge, 
where  the  oil  film  is  thickest,  and  escapes  at  the  trailing  edge, 
where  the  oil  film  is  exceedingly  thin.  Some  oil  also  escapes 
along  the  sides  of  the  pad,  as  indicated  in  Fig.  47  which  shows 
the  directions  of  oil  flow.  These  interesting  photographs  are 
reproduced  by  the  courtesy  of  W.  J.  Hamilton  Gibson,  more 
details  being  given  in  his  paper  before  "The  Institution  of  Naval 
Architects/'  April,  1919. 

In  some  interesting  experiments  made  by  Brown,  Beven  & 
Co.  the  effect  of  slightly  rounding  the  leading  edge  of  the  pads 
was  found  to  be  an  increased  carrying  power  and  a  slight  shifting 


FIG.  48.— Miehell  marine  thrust  bearing. 

further  aft  of  the  centre  of  pressure;  these  experiments  also 
confirmed  Mr.  Michell's  opinion  as  regards  the  shape  of  the  pads, 
which  should  be  approximate^  square  to  give  the  best  results. 

The  pads  are  usually  white  metalled,  and  ore  might  ask,  why 
go  to  this  trouble,  as  there  is  no  metallic  contact.  The  character 
of  the  metal  of  the  lubricated  surfaces  ought  not  to  influence  the 
results,  as  long  as  they  are  strong  enough  to  stand  the  pressure; 
fine  particles  of  grit  or  dirt  may  however  get  carried  in  between 
the  surfaces  with  the  oil;  in  that  case  the  white  metal  will  get 
abraded,  and  this  is  preferable  to  injuring  the  collar,  which  would 
occur  were  the  pads  made  of  hard  material. 

The  thickness  of  the  oil  film  is  very  thin,  sometimes  less  than 
0.001  inch,  so  that  the  bearing  surfaces  must  be  carefully  scraped 
and  oil  grooves  must  on  no  account  be  cut,  as  they  will  allow  the 
oil  to  escape  and  prevent  proper  film  formation. 

The  heat  generated  in  the  bearing  is  entirely  due  to  internal 
fluid  friction  in  the  oil  film,  there  being  no  metallic  contact; 


PLAIN  THRUST  BEARINGS 


173 


the  frictional  heat  is  therefore  dependent  upon  the  area  of  the 
thrust  pads,  the  rubbing  speed  and  the  viscosity  of  the  lubricant. 
The  makers  supply  particulars  as  to  the  amount  of  heat  generated 
under  specific  conditions  and  the  quantity  of  oil  and  cooling  water 
required  to  give  the  best  results. 

The  number  of  pads  may  vary,  but  is  usually  six.  They  may 
be  arranged  in  the  form  of  an  inverted  horseshoe,  as  in  the  self- 
contained  marine  thrust  bearing  (Fig.  48)  suitable  both  for  geared 
turbines  and  marine  steam  engines;  or  evenly  distributed  over 
the  collar,  as  in  the  geared  turbine  thrust  bearing  Fig.  49. 

In  Fig.  48  the  collar  bears  against  two  inverted  horseshoe  shaped 
surfaces  (one  for  ahead  and  one  for  astern  thrust).  Each  of 
these  surfaces  is  subdivided  into  six  pads  pivoted  on  the  ends  of  a 


FIG.  49. — Michell  turbine  thrust  bearing. 

corresponding  number  of  screws.  The  shaft  is  supported  by  two 
ordinary  journal  bearings,  and  the  well  in  which  the  collar  revolves 
is  filled  about  half  full  of  oil,  which  lubricates  the  blocks;  the 
journal  bearings  have  upper  keeps,  fitted  with  syphon  oilers,  and 
a  light  sheet  iron  cover  forms  a  dust  shield. 

The  housing  consists  of  one  main  casting  and  is  water  jacketed 
in  large  size  bearings,  or  when  the  speed  is  high. 

In  Fig.  49  the  shaft  is  carried  in  two  journal  bearings,  the  same 
as  in  Fig.  48,  but  the  housing  is  made  in  halves,  and  the  blocks 
instead  of  being  independently  adjusted  are  mounted  in  spherical 
seats  and  adjust  themselves  automatically.  This  type  of  bearing 
is  not  self-contained  as  in  Fig.  48,  but  must  be  connected  to  an 
oil  circulation  system,  usually  a  branch  from  the  main  turbine 


174  PRACTICE  OF  LUBRICATION 

oiling  system.  The  blocks  may  be  either  "line  pivoted"  on 
the  spherical  seats,  or  "point  pivoted,"  as  shown. 

For  steam  turbines,  where  the  thrust  bearing  is  combined  with 
the  main  bearing  at  the  high  pressure  end,  and  when  the  thrust 
does  not  exceed  5,000  lb.,  a  much  simpler  form  of  Michell 
bearing  is  designed,  one  type  having  only  one  pivoted  pad  on 
either  side  of  the  collar.  The  Michell  thrust  bearing  is  also 
used  with  great  success  as  vertical  thrust  bearings,  required 
for  vertical  water  turbines,  centrifugal  pumps,  vertical  electric 
generators,  etc. 

It  will  be  recognized  that  a  perfect  oil  film  cannot  be  established 
in  the  ordinary  form  of  thrust  bearing  in  which  the  coefficient  of 
TrictiorT  is  about  0.03, whereas  in  the  Michell  bearing  it  falls  to 
0.002  or  even  less.  The  Michell  thrust  bearings  will  safely  carry 
a  load  of  400-500  lb.  per  square  inch  with  rubbing  speeds  from 
60  ft.  to  100" ft.  per  second,  without  danger  of  metallic  contact. 
Michell  thrust  bearings  have  run  with  no  abnormal  heat,  carry- 
ing a  pressure  of  five  tons  per  square  inch  at  which  pressure  the 
white  metal  surfaces  of  the  pads  began  to  flow  like  butter,  thus 
showing  that  with  perfect  film  formation  tfre  oil  film  will  stand 
enormous  pressures. 

The  Kingsbury  thrust  bearing  is  designed  on  very  much  the 
same  lines  as  the  Michell  bearing.  Prof.  Kingsbury  also  divides 
the  supporting  surface  in  segmental  pads,  and  the  pads  are  made 
self -adjustable  by  rounding  the  supporting  surface,  as  shown  in 
Fig.  50.  The  pad  (2)  rocks  over  the  support  (3)  and  thus  allows 
a  wedge  shaped  perfect  oil  film  to  form  between  the  pad  and  the 
revolving  collar  (1).  Large  Kingsbury  bearings  for  supporting 
the  vertical  generating  units  at  the  McCalls  Ferry  plant  of  the 
Pennsylvanian  Water  Power  Company  were  reported  in" Power" 
to  give  the  following  results : 

Outside  diameter  of  collar,  inches 48 

Total  load  on  bearing,  pounds 410,000 

Area  of  shoes,  square  inches 1,160 

Unit  pressure  per  square  inch,  pounds 350 

Revolutions  per  minute 94 

Mean  surface  speed,  ft.  per  min 900 

Oil  flow  through  bearing  per  min.,  gallons 15 

Kind  of  oil ' Light  mineral 

Mean  temperature  rise  of  oil  in  bearing,  deg.  F.  4.5 

Frictional  loss  in  bearing,  H.P 9 

Coefficient  of  friction .  0.0008 

The  oils  used  for  Michell  thrust  bearings  are  mineral  oils  of 
suitable  viscosity.  There  is  no  need  for  compounded  oils,  as 
the  film  formation  is  not  influenced  by  the  oiliness  of  the  oil. 


PLAIN  THRUST  BEARINGS 


175 


All  that  is  required  is  viscosity.  For  slow  speed  conditions, 
viscous  oils  are  required,  like  Bearing  Oil  No.  4  or  Circulation 
Oil  No.  3;  for  high  speed  conditions,  as  in  steam  turbines,  the 


FIG.  50. — Kingsbury  thrust  pad. 

same  turbine  oil  is  employed  for  the  Michell  thrust  as  for. the 
turbine  bearings. 

Compounded  marine  engine  oils  may  be  used  for  steam  engine 
thrust  bearings  for  the  sake  of  simplicity,  but  straight  mineral 
oils  operate  cleaner,  and  should  be  preferred. 


CHAPTER  XII 
BALL  AND  ROLLER  BEARINGS 

Ball  and  roller  bearings  operate  on  different  principles  from 
plain  bearings;  the  rolling  contact  between  the  balls  or  rollers  and 
the  stationary  or  revolving  surfaces  (ball  races,  roller  races) 
is  theoretically  only  point  contact  in  ball  bearings,  and  line 
contact  in  roller  bearings,  whereas  ordinary  bearings  have 
large  surfaces  in  rubbing  contact  at  all  times.  When  machinery 
equipped  with  ordinary  bearings  is  started  the  frictional  resis- 
tance is  great,  several  times  as  great  as  the  resistance  after  a  couple 
of  revolutions  when  the  oil  film  has  been  established;  whereas 
in  ball  and  roller  bearings  the  friction  at  starting  is  the  same  as 
or  only  very  little  more  than  the  friction  during  operation,  and 
is  always  lower  than  in  plain  bearings. 

It  is  this  great  advantage  that  ball  and  roller  bearings  have 
over  plain  bearings  which  is  chiefly  responsible  for  their  ever 
widening  use,  particularly  in  machinery  that  frequently  starts 
and  stops  or  changes  its  direction  of  rotation,  such  as  auto- 
mobiles, motor  cycles,  bicycles,  reversible  electric  motors, 
railway  turn  tables,  etc. 

Roller  bearings  may  possibly  stand  rough  usage,  vibration 
and  shocks  better  than  ball  bearings,  but  they  will  not  carry 
heavier  loads,  as  many  people  seem  to  think,  and  at  very  high 
speeds  ball  bearings  are  usually  preferred.  Prof.  Goodman  has 
made  a  lengthy  study  of  ball  and  roller  bearings,  and  the  fol- 
lowing remarks  are  largely  based  on  the  information  given  by  him 
in  papers  read  before  the  Institution  of  Civil  Engineers,  1911- 
12,  and  the  Institution  of  Automobile  Engineers,  in  1913. 

ROLLER  BEARINGS 

The  rollers  are  nearly  always  plain  cylindrical.  An  inex- 
pensive roller  bearing  is  the  Koppel  bearing  shown  in  Fig.  51. 
It  has  no  cage  and  the  ends  of  the  rollers  are  rounded.  Most 
bearings  have  a  cage,  as  in  Fig.  52  to  hold  the  rollers  in  position. 

The  Hyatt  bearings  (Fig.  53)  have  rollers  which  are  helical 
springs,  alternately  of  right-  and  left-hand  pitch,  and  are  much 
used  for  line  shafting. 

176 


BALL  AND  ROLLER  BEARINGS 


177 


In  the  Kynoch  bearing  the  rollers  (Fig.  54)  are  tubular  rolled 
from  a  special  steel  stamping  to  avoid  a  longitudinal  joint. 

The  bearing  in  Fig.  55  has  short  rollers  one  diameter  in  length; 
when  hardened  and  ground  with  the 
same  degree  of  accuracy  as  the  best 
ball  bearings  this  bearing  gives  ex- 
cellent results. 

The  Timken  roller  bearing  (Fig. 
56)  has  two  rows  of  tapered  rollers 
and  is  largely  used  for  automobiles. 

Fig.  57  shows  a  roller  thrust  bear-  _ 

FIG.  51. — Koppel   roller  bearing. 

mg  with  tapered  rollers. 

The  pressure  on  the  narrow  line  of  contact  between  roller 
and  shaft  is  great;  hence,  soft  materials  are  liable  to  be  crushed 
and  the  wear  is  excessive.  For  high  pressures  the  rollers,  sleeve, 


FIG.  52. — Roller  bearing  cage. 


FIG.  53. — Hyatt  rollers. 


and  casing  liner  should  be  steel,  hardened  and  ground  so  as  to 
minimize  the  wear. 

During  operation  the  roller  cage  moves  at  approximately  half 
the  journal  speed,  and  the  rollers  revolve  at  very  high  speed, 


FIG.  54. — Kynoch  roller. 


FIG.      55. — Short     roller 
bearing. 


rubbing  with  their  ends  against  the  cage,  so  that  these  points 
require   lubrication,   more  especially  because  the  rollers  often 


f78 


PRACTICE  OF  LUBRICATION 


create  considerable  end  thrust.  As  such  end  thrust  forces  the 
cage  against  the  inside  of  the  bearing  housing,  lubrication  is 
also  required  for  these  additional  rubbing  surfaces. 


FIG.   56. — Timken  roller  bearing. 

When  the  rollers  are  not  absolutely  parallel  with  the  shaft  or  if 
they  are  the  least  bit  taper,  or  if  the  shaft  or  sleeve  against  which 
they  revolve  is  taper  the  rollers  tend  to  roll  in  a  helical  path. 
They  push  themselves  against  one  end  of  the  casing  until  the 

pressure  becomes  sufficiently  great, 
then  they  slip  back  suddenly  and 
start  rolling  afresh  in  a  helical  path 
toward  the  same  end  of  the  casing 
as  before.  The  amount  of  end. 
thrust  created  is  largely  dependent 
upon  the  bearing  load  (it  may  be 
as  high  as  30  per  cent,  of  the  load) 
and  does  not  appear  to  vary  with 
the  amount  the  rollers  are  out  of 
truth. 

The  rollers  have  been  known  to 
right    through    their   casing 


FIG. 


57. — Roller    thrust    bearing 
tapered  rollers. 

wear 
and  nearly  through  the  housing  itself. 

With  change  in  direction  of  rotation  the  endthrust  is  always 
reversed.  Speaking  generally,  the  starting  effort  of  roller  bearings 
is  only  slightly  greater  than  the  running  effort,  but  when  there 


BALL  AND  ROLLER  BEARINGS  179 

is  considerable  end  thrust  the,  starting  effort  may  be  even  twice 
as  great  as  the  running  effort. 

The  main  evils  of  end  thrust  in  roller  bearings  are : 

1.  It  is  largely  the  cause  of  the  frictional  resistance. 

2.  It  causes  excessive  wear  on  rollers,  cage,  shaft  and  casing. 

3.  It  causes  the  bearing  to  run  hot. 

4.  It  sets  up  vibration  and  rumbling  in  the  bearing  and  its 
housing. 

The  makers  of  the  Hyatt  roller  bearings  claim  that  one-half 
of  the  helical  rollers  will  tend  to  run  toward  one  end  of  the  casing 
and  the  other  half  toward  the  other  end,  and  that  end  thrust 
is  therefore  eliminated.  Prof.  Goodman  found  that  this  was 
largely  true  and  that,  although  the  loads  they  carried  were  very 
small  as  compared  with  high-class  roller  or  ball  bearings,  yet 
they  were  very  successful  for  ordinary  purposes,  line  shafting 
in  particular. 

In  properly  designed  roller  bearings,  when  there  is  little  or  no 
end  thrust,  the  friction  is  practically  independent  of  lubrication, 
but  with  a  large  amount  of  end  thrust  lubrication  makes  a  great 
difference,  for  the  reason,  that  when  there  is  no  end  thrust  there 
is  pure  rolling  action,  but  when  end  thrust  exists  there  is  friction 
between  the  cage  and  the  casing.  This  friction  decreases 
somewhat  at  high  speeds  because  of  the  better  oil  film — less 
metallic  contact — so  that  in  roller  bearings  with  end  thrust  the 
coefficient  of  friction  is  inclined  to  decrease  at  high  speeds, 
whereas  in  roller  bearings  with  pure  rolling,  it  is  practically 
independent  of  the  speed. 

Speaking  generally,  roller  bearings,  even  the  simplest  types, 
develop  less  friction  than  plain  bearings,  provided  of  course 
that  they  are  erected  with  a  reasonable  amount  of  care.  Bearing- 
housings  should  be  self  aligning,  so  as  not  to  set  up  undue  stresses 
anywhere  in  the  bearings. 

To  insure  the  best  results  both  ball  and  roller  bearings  must  be 
very  accurately  fitted  and  if  worn  must  be  renewed  and  not 
allowed  to  run.  If  they  are  slightly  out  of  line  or  slightly  worn, 
great  stresses  are  set  up;  the  friction  is  high,  may  even  be  higher 
than  with  plain  bearings,  and  the  balls  or  rollers  may  break. 

The  coefficient  of  friction  of  roller  bearings  is  always  higher  for 
small  than  for  high  loads,  and  considerably  increased  when  there 
is  appreciable  end  thrust.  The  coefficient  of  friction  ranges 
from  0.002  to  0.007;  only  for  highly  finished  short  rollers  and  bear- 
ings with  little  or  no  end  thrust  as  the  bearing  indicated  by  Fig. 
55,  has  the  coefficient  of  friction  fallen  below  0.002,  but  then  such 
a  bearing  approaches  in  action  the  ball  bearing,  as  also  in  the  great 


180  PRACTICE  OF  LUBRICATION 

accuracy  of  its  workmanship.  The  normal  average  values  for  the 
coefficient  of  friction  may  be  taken  as  0.003  to  0.004;  but  for 
bearings  of  the  Hyatt  and  Kynoch  types,  the  values  are  higher, 
ranging  from  0.0045  to  0.007,  the  lower  values  corresponding  to 
high  loading. 

Prof.  Goodman  summarizes  the  general  results  of  his  tests  of 
roller  bearings  as  follows: 

1.  The  coefficient  of  friction  of  roller  bearings  is  greater  at  low  than 
at  high  loads,  but  it  is  much  more  nearly  constant  that  it  is  in  plain, 
lubricated  bearings. 

2.  The  coefficient  of  friction  of  roller  bearings  in  which  there  is  pure 
rolling  is  very  nearly  constant  at  all  speeds,  but  when  there  is  end 
thrust,  the  friction  decreases  as  the  speed  increases. 

3.  The  coefficient  of  friction  is  independent  of  the  temperature  of 
the  bearings  unless  the  end  thrust  is  excessive. 

4.  The  starting  effort  is  very  little  greater  than  the  running  effort. 

5.  The  friction  in  a  well-designed  bearing  is  not  greatly  affected  by 
lubrication. 

6.  The  wear  of  the  rollers  is  often  excessive  if  the  whole  of  the 
rotating   parts   and   the    casing  are  not  hardened  and  well  finished, 
especially  when  the  bearing  shows  end  thrust. 

7.  The  end  thrust  on  the  rollers  varies  almost  directly  as  the  load 
on  the  bearing,  and  usually  diminishes  as  the  speed  increases.     The 
direction  of  the  thrust  is  usually  reversed  when  the  direction  of  rotation 
is  reversed. 

8.  Other   things   being  equal,   the  frictional  resistance  of  bearings 
fitted  with  large  rollers  is  less  than  with  small  rollers. 

9.  The  safe  load  for  a  given  bearing  diminishes  as  the  speed  of  rotation 
of  the  rollers  increases. 

BALL  BEARINGS 

Ball  bearings  cannot  create  end  thrust;  herein  lies  one  of  their 
great  advantages  over  roller  bearings,  particularly  at  high  speeds. 
They  are  less  inclined  to  heat  than  roller  bearings,  as  the  friction 
is  lower.  The  starting  effort  is  the  same  as  the  running  effort, 
and  in  consequence  ball  bearings,  notwithstanding  that  they  have 
only  point  contact  as  compared  with  line  contact  in  roller  bear- 
ings, are  able  to  sustain  as  heavy  loads  as  roller  bearings. 

Ball  bearings  must  not  be  adjustable;  once  the  bearing  is 
assembled,  all  running  clearances  must  be  correct,  and  neither 
the  balls  nor  the  races  must  wear. 

Four-point  contact  and  three-point  contact  bearings  (Figs. 
58  and  59)  are  not  so  satisfactory  as  two-point  contact  bearings 
(Fig.  60)  for  the  reason  that  there  is  a  grinding  action  between 
the  balls  and  the  races,  and  the  balls  get  scratched.  Two-point 


BALL  AND  ROLLER  BEARINGS 


181 


contact  bearings  may  have  flat  races  as  Fig.  00  and  the  results 
are  very  satisfactory;  in  fact,  the  coefficient  of  friction  is  lower 
than  in  other  types  of  bearings,  but  the  load-carrying  capacity  i« 
2  to  21^  times  greater  with  grooved  races,  as  in  Fig.  61.  With 


FIG.  58.— Four  point  con-   FIG.  59. — Three  point  con-   FIG.       60. — Two     point 
tact  ball  bearing.  tact  ball  bearing.  contact  ball  bearing. 

flat  races  the  coefficient  of  friction  decreases  with  increase  in 
load,  but  with  grooved  races  it  may  increase,  possibly  due  to  the 
increased  area  of  metallic  contact  between  the  balls  and  the  races. 
For  heavy  loads  the  grooved  races  are  to  be 
preferred,  given  good  alignment  and  workman- 
ship; but  if  there  is  any  doubt  as  to  these 
points,  flat  (or  cylindrical)  races  may  prove 
better,  as  a  slight  lack  of  alignment  will  not 
affect  the  balls  on  a  flat  surface,  but  may 
cause  them  to  jamb  and  get  cracked  when 
running  in  grooved  races. 

Prof.  Goodman  has  found  that  the  friction 
in  ball  bearings  is  never  reduced  by  lubrica- 
tion but  is  sometimes  greater  than  when  the 
bearings  run  dry.  Bearings  with  flat  races 
have  run  dry  for  long  periods  without  any 
apparent  ill  effects;  but  bearings  with  grooved 
races  soon  begin  to  whistle  and  grind,  pro- 
bably because  there  is  more  actual  rubbing 
between  the  balls  and  the  grooves  than  with 
flat  races.  As,  however,  the  absence  of  lubri- 
cant means  that  the  surfaces  in  time  will  rust, 
which  is  fatal,  lubrication  is  always  provided. 

It  is  important  that  the  balls  shall  be  all  of  the  same  size;  if 
some  of  the  balls  are  smaller  than  others,  the  big  balls  have  to 
take  more  than  their  share  of  the  load  (being  bigger  they  get 
more  squeezed  than  the  little  ones);  the  smaller  balls  take  less 


FIG.  6  1  .  —  B  a  1 1 
bearing  with  grooved 
race. 


182 


PRACTICE  OF  LUBRICATION 


than  their  share,  therefore  slip  more,  and  it  is  this  slipping  which 
causes  the  balls  to  deteriorate  and  get  scratched. 

All  the  best  makers  will  guarantee  first-class  balls  to  be  ac- 
curate within  one  ten-thousandth  of  an  inch;  it  does  not  matter 

much  whether  1-inch,  balls  are 
slightly  more  or  less  than  1  inch  in 
diameter,  but  they  must  all  be  ex- 
actly alike,  and  with  properly  made 
bearings  the  wear  will  then  be  prac- 
tically nil. 

When  balls  are  overloaded  they 
become  covered  with  tiny  flakes  of 
"snow, "  the  flakes  being  tiny  crys- 
tals which  have  broken  away  from 
the  surface  of  the  ball;  these  specks 
FIG.  62.— Multiple  ring  ball  can  only  be  seen  under  the  micro- 
scope with  300  to  400  diameters 

magnification.  When  a  ball  finally  breaks  down  it  peals  on  one 
hemisphere,  and  curiously  enough  usually  only  on  the  one 
hemisphere. 

For  very  heavy  loads  multiple  ring  bearings  may  be  employed, 
as  the  four-ring  radial  bearing  in  Fig.  62.     In  order  to  ensure 


FIG.  63. — Skefko  two  row  ball  bearing. 

that  each  ring  shall  carry  its  proper  share  of  the  load,  a  sheet 
of  linoleum  is  placed  between  the  housing  and  the  races.  This 
same  principle  can  also  be  applied  to  thrust  bearings  with  mul- 
tiple rows  of  balls,  as  in  Fig.  63,  which  shows  a  railway 


BALL  AND  ROLLER  BEARINGS 


183 


turntable  fitted  with  a  Skefko  two-row  ball  bearing.  A  brass 
shield  fitted  round  the  lower  bearing  housing  retains  the  lubri- 
cating grease,  which  fills  the  bearing  and  keeps  the  dirt  out. 

The  question  of  alignment  of  ball  bearings  is  as  important  as 
in  the  case  of  roller  bearings,  if  not  more  so. 
The  bearing  housings  are  therefore  usually 
made  self  aligning,  but  in  one  type  of  bearing, 
the  " Skefko"  ball  bearing,  the  spherical  outer 
ball  race  (Fig.  64)  allows  the  inner  race  and  balls 
to  swivel  out  of  their  plane  of  rotation,  so  that 
they  can  adjust  themselves  to  any  lack  of  align- 
ment of  the  shafting,  whether  owing  to  bending 
or  bad  erection,  and  the  adjustment  will  of 
course  take  place  with  much  greater  ease  than 
in  the  case  of  a  self-aligning  bearing  housing. 

This  bearing  has  other  features.  As  there 
are  two  rows  of  balls  the  load  is  distributed  at 
any  instant  over  three  balls  instead  of  on  one 
or  two  balls,  as  in  an  ordinary  ball  bearing;  this 
feature  increases  the  load  carrying  capacity. 
The  bearing  is  also  capable  of  taking  a  certain  1 

,  FIG.     64. — Skefko 

amount  of  end  thrust,  as  the  balls  touch  the      swivel  bearing. 

spherically  shaped  outer  race  at  points  where 

the  pressure  between  them  is  at  a  slight  angle  with  the  vertical 

plane. 

The  inner  race  of  a  ball  bearing  must  not  be  slack  on  the  shaft; 
the  .shaft  should  preferably  be  ground  to  a  light  tapping  fit  for 


FIG.  65. — Ball  bearings  for  electric  motor. 

the  inner  race  and  the  bearing  secured  against  a  shoulder  by 
means  of  a  nut  (see  Fig.  65).  The  outer  race  must  not  be  a 
driving  fit  in  the  housing,  but  should  have  an  easy  sliding  fit, 
as  otherwise  the  balls  will  be  unevenly  loaded. 


184  PRACTICE  OF  LUBRICATION 

Fig.  65  shows  the  correct  method  of  mounting  ball  bearings  on 
an  electric  motor;  the  right-hand  outer  race  is  not  allowed  much 
movement  between  the  housing  covers  but  the  left-hand  outer 
race  has  freedom  to  slide  in  its  housing  when  the  shaft  expands 
or  contracts. 

The  coefficient  of  friction  of  ball  bearings  is  always  greater  with 
small  than  with  high  loads;  it  ranges  from  0.001  to  0.003,  the  nor- 
mal average  value  being  0.0015  to  0.002. 

Prof.  Goodman  summarizes  the  results  of  his  tests  of  ball  bear- 
ings as  follows,  and  his  interesting  remarks  concerning  a  compari- 
son between  ball  and  roller  bearings  are  also  quoted: 

LAWS  OF  BALL-BEARING  FRICTION 

1.  The  coefficient  of  friction  of  ball  bearings  with  flat  races  decreases, 
and  with  grooved  races  sometimes  increases,  as  the  load  is  increased;, 
but  it  is  much  more  constant  than  that  of  plain,  lubricated  bearings. 

2.  The  coefficient  of  friction  of  ball  bearings  is  practically  constant 
at  all  speeds,  but  has  a  slight  tendency  to  decrease  as  the   speed  is 
increased. 

3.  The  coefficient  of  friction  is  independent  of  the  temperature  of 
the  bearing. 

4.  The  starting  effort  is  practically  the  same  as  the  running  effort. 

5.  The    friction  in  a  well-designed  bearing  is  very  slightly  higher 
when  the  bearing  is  lubricated  than  when  it  is  dry,  but  in  badly  designed 
bearings  the  friction,  when  they  are  lubricated,  is  lower  than  when  they 
run  dry. 

6.  The  wear  on  the  balls  when  they  are  not  overloaded  is  extremely 
small  and  is  almost  negligible. 

7.  There  is  no  end-thrust  on  ball  bearings. 

8.  Other   things   being  equal,   the   frictional   resistance   with   large 
balls  is  less  than  with  small  balls. 

9.  The  safe  load  for  a  given  bearing  diminishes  as  the  speed  of  rota- 
tion of  the  bails  is  increased. 

COMPARISON  OF  BALL  AND  ROLLER  BEARINGS 

Friction. — In  general,  the  friction  of  ball  bearings  is  considerably 
less  than  that  of  roller  bearings,  but  both  are  very  much  better  in  this 
respect  than  plain  bearings  with  ordinary  lubrication. 

The  coefficient  of  friction  of  ball  bearings  is  slightly  less  than  that 
of  plain  bearings  running  in  a  bath  of  oil. 

End  Thrust. — There  is  no  end  thrust  on  ball  bearings,  but  in  many 
roller  bearings  it  is  often  quite  serious  in  amount. 

Space  Occupied. — Most  roller  bearings  are  longer  for  a  given  load 
carrying  capacity  than  ordinary  plain  bearings.  Fig.  55  is  an  exception 
but  ball  bearings  are,  as  a  rule,  much  shorter  and  occupy  much  less 


BALL  AND  ROLLER  BEARINGS  185 

space  than  even  the  best  plain  bearings.  There  is,  however,  an  excep- 
tion in  the  case  of  bearings  for  connecting  rod  ends. 

Cost. — Roller  bearings,  as  a  rule,  do  not  cost  much  more  than  plain 
bearings  designed  to  carry  the  same  load,  but  ball  bearings  and  roller 
bearings  of  the  best  quality  cost  three  to  four  times  as  much. 

In  electrical  machinery  it  is  often  found  that  when  ball  bearings  are 
used  the  length  and  diameter  of  the  armature-shaft  may  be  materially 
reduced,  as  well  as  the  length  of  the  bed,  owing  to  the  fact  that  ball 
bearings  are  so  much  shorter  than  ordinary  bearings;  the  net  result  is 
that  the  cost  of  the  machine  is  little  if  any  greater  than  when  plain 
bearings  are  used. 

Shafting  Mounted  on  Ball  Bearings. — For  long  lines  of  shafting, 
carrying  pulleys  and  couplings,  ball  bearings  are  not  so  convenient 
as  roller  bearings.  If  a  ball  bearing  on  such  a  shaft  fails,  it  is  impossible 
to  replace  the  ball  races  without  taking  down  at  least  one  length  of 
the  shafting,  removing  the  couplings  and  pulleys,  and  fitting  a  new 
bearing.  But  with  roller  bearings,  which  are  often  used  without  a 
sleeve,  there  is  no  difficulty  in  replacing  the  whole  bearing  or  any  part 
of  it  without  disturbing  the  shafting,  because  both  cage  and  bearing 
liner  are  nearly  always  made  in  halves,  a  practice  quite  out  of  the  ques- 
tion with  ball  bearings,  in  which  extreme  accuracy  is  required. 

With  long  lines  of  shafting  provision  must  be  made  for  the  expansion 
and  contraction  of  the  shaft.  When  plain  (i.e.,  not  grooved)  bearings 
are  used  there  is  no  difficulty,  but  with  grooved  bearings  the  outer  ring 
must  be  mounted  in  a  housing  in  which  it  can  slide.  The  efficiency  of 
power  transmission  by  shafting  mounted  on  ball  bearings  is  higher  than 
can  be  obtained  by  any  other  known  means. 

LUBRICATION  OF  BALL  AND  ROLLER  BEARINGS 

On  page  178  the  various  forms  of  friction  which  exist  in  a 
roller  bearing  are  outlined,  and  it  is  obvious  that  in  most  roller 
bearings,  owing  to  existing  or  possible  end  thrust,  lubrication 
must  be  provided  to  reduce  friction  between  the  various  rubbing 
surfaces. 

In  ball  bearings  there  is  less  friction  because  of  the  absence  of 
end  thrust,  but  there  is  a  certain  amount  of  friction  between  the 
balls  and  the  sides  of  the  cage  pockets  in  which  they  revolve. 
One  form  of  friction  which  exists  both  in  ball  and  roller  bearings 
has  not  yet  been  touched  upon;  it  is  due  to  the  fact  that  balls, 
rollers  and  races  are  somewhat  elastic,  and  that  consequently 
instead  of  point  and  line  contact  we  actually  get  metallic  contact 
over  a  small  circular  and  rectangular  area  for  balls  and  rollers 
respectively.  The  metal  in  front  of  and  behind  a  roller,  for  ex- 
ample, is  pushed  up  as  shown  exaggerated  in  Fig.  66,  the  surface 
of  the  race  is  slightly  stretched  where  it  touches  the  roller,  and 


186 


PRACTICE  OF  LUBRICATION 


when  the  metallic  contact  ceases  the  surface  contracts.  At 
this  point  a  certain  small  amount  of  rubbing  therefore  takes  place 
between  the  roller  and  the  race.  It  will  be  recognized  that  in 
front  of  the  roller  a  similar  small  amount  of  rubbing  takes  place, 
as  the  surface  of  the  race  coming  Into  contact  with  the  roller 
becomes  stretched.  It  will  be  seen  that  the  stretching  and  the 
unstretching  of  the  race  in  front  of  and  behind  the  roller  both 
tend  to  impede  the  progress  of  the  roller  and  therefore  create 
resistance. 

When  the  surfaces  of  the  balls  or  rollers  and  races  are  very 
hard  and  lack  elasticity,  this  kind  of  friction  is  less  than  with 
more  elastic  surfaces,  but  is  always  very  small.  Lubrication  of 
these  points  is  difficult,  as  the  pressures  must  be  very  great; 
but  even  if  lubrication  of  the  roll- 
ing surfaces  makes  them  more 
slippery,  it  must  not  be  overlooked 
that  compared  with  dry  surfaces 
we  are  adding  a  certain  amount  of 
fluid  friction.  It  is  a  fact  that 
the'total  amount  of  friction  remains 
very  much  the  same  whether  the 
surfaces  are  lubricated  or  not. 


FIG.  66.— Rolling  friction. 


FIG.    67. — Vertical  ball  bearing, 
with  oil  bath  lubrication. 


As  has  already  been  mentioned,  lubrication  of  ball  and  roller 
bearings  is  imperative  to  prevent  rusting  and  to  maintain  the 
balls,  rollers  and  races  in  a  clean  and  highly  polished  condition. 
The  entrance  of  moisture  and  dust  must  also  be  avoided,  so  that 
in  humid  or  dirty  surroundings  the  bearings  must  have  efficient 
dust  guards,  or  they  must  be  completely  filled  with  lubricating 
grease.  In  the  latter  case  a  fillet  of  grease  will  be  formed  at 
either  end  which  seals  the  bearing  against  the  entrance  of  dust 
and  moisture. 

Fig.  67  shows  the  application  of  a  ball  guide  bearing  to  a 
vertical  shaft;  the  housing  is  formed  as  an  oil  reservoir,  and  dur- 
ing operation  centrifugal  action  forces  the  oil  to  rise  and  lubricate 
the  balls. 


BALL  AND  ROLLER  BEARINGS 


187 


Fig.  68  shows  a  vertical  ball  thrust  bearing  fitted  for  grease 
lubrication;  with  slight  alteration  this  bearing  could  also  be 
designed  with  oil  lubrication  without  danger  of  oil  overflowing 
down  the  shaft. 


FIG.  68. — Vertical  ball  thrust  bearing. 

Fig.  69  shows  a  ball  thrust  bearing  which  may  be  used  horizont- 
ally or  vertically,  and  in  which  the  shaft  is  allowed  to  swivel 
slightly  on  the  surfaces  indicated  by  the  dotted  circular  line. 
These  surfaces  are  ground  and  are  submerged  in  oil.  This 


FIG.  69. — Self-adjusting  ball  thrust  bearing. 

arrangement  will  permit  slight  self-adjustment,  and  make  the 
running  easier. 

Fig.  70  shows  an  axlebox  with  a  Skefko  ball  bearing  as  used  on 
a  Swedish  railway   (Karlsbad-Munkfors  Railway).     The  axle- 


188 


PRACTICE  OF  LUBRICATION 


box  is  completely  filled  with  grease,  and  it  has  not  been  found 
necessary  to  inspect  and  replenish  with  grease  more  than  once 
or  twice  a  year. 

Fig.  71  shows  a  ball  footstep  bearing  used  for  mortar  mills  in 
India,  grinding  refractory  material.  The  dust  is  very  hard  and 
is  kept  out  from  the  bearing  by  means  of  an  oil  seal,  as  shown, 

which  can  be  removed  for  cleaning 
purposes.  These  bearings  are  re- 
ported to  give  complete  satisfac- 
tion. 

It  is  extremely  important,  when 
handling  ball  or  roller  bearings 
to  prevent  dirt,  filings,  etc.  from 
getting  into  them;  many  failures 
of  bearings  have  been  caused  by 
carelessness  of  this  kind.  When, 
for  example,  bearings  are  cleaned 
in  the  average  motor  car  repair 
shop,  they  are  often  dipped  in 
dirty  kerosene  full  of  all  sorts  of  sediment  and  impurities  which 
get  stirred  up  when  the  bearings  are  " cleaned." 

A  good  cleaning  agent  is  made  from  soda  and  boiling  water 
(1  Ib.  of  soda  to  25  Ibs.  of  water);  the  bearings  may  be  dipped 
several  times  to  remove  all  grease  and  dirt,  then  immersed  in 


FIG.  70. — Skefko  railway  axle  box. 


FIG.  71. — Oil  sealed  ball  footstep  bearing. 

clean  kerosene  and  given  a  swirling  motion  when  all  surfaces 
should  appear  bright  and  clean.  » 

Many  automobile  bearings  have  been  ruined  by  wearings  from 
the  gears  or  impurities  introduced  when  the  gear  case  or  rear  axle 
case  has  had  its  lid  removed  for  inspection.  Hence  the  design 
of  oil  filler  as  shown  in  Fig.  191,  page  482,  is  to  be  recommended, 
also  from  the  point  of  view  of  the  safety  of  the  ball  or  roller 
bearings,  now  so  frequently  employed  in  gear  box  or  rear  axle 
constructions. 


BALL  AND  ROLLER  BEARINGS  180 

When  washing  motor  cars  with  water  at  great  pressure,  it  is 
quite  easy  for  the  water  to  enter  some  of  the  bearings  (which  may 
not  be  completely  filled  and  sealed  with -grease)  and  cause  rusting, 
with  the  almost  inevitable  result  that  the  bearings  are  destroyed. 

As  to  whether  oil  or  grease  is  to  be  employed,  it  appears  to  be 
preferable,  wherever  the  surrounding  air  is  reasonably  clean  and 
not  too  humid,  to  use  oil.  The  fitting  of  a  dust  guard  in  the  form 
of  a  felt  packing  is  always  advisable;  the  oil  keeps  the  balls 
clean  and  must  be  an  acid-free,  pure  mineral  oil  so  as  not  to  gum 
or  corrode  the  surfaces.  It  should  be  sufficiently  viscous  not 
to  cause  excessive  oil  spray,  but  oil  spray  may  also  be  caused  by 
overfilling  the  bearings.  As  the  friction  in  ball  bearings  is  not 
influenced  by  the  viscosity  of  the  oil,  the  selection  of  oil  may  be 
entirely  governed  by  the  other  conditions  mentioned;  of  course 
when  the  oil  is  carried  to  the  surfaces  by  centrifugal  action  it 
must  not  be  too  viscous,  and  at  low  temperatures  the  oil  must 
have  a  reasonably  low  setting  point,  so  as  not  to  congeal  in  the 
bearings. 

.In  roller  bearings,  particularly  those  in  which  a  certain  amount 
of  end  thrust  is  created,  mineral  oils  of  heavy  viscosity  must  be 
used  for  high  temperatures,  for  low  speeds  or  heavy  loads,  to 
minimize  wear.  Compounded  oils  would  give  better  lubrication 
than  mineral  oils,  but  must  not  be  used  for  the  reasons  mentioned 
above. 

When  bearings  are  exposed  to  high  room  temperatures,  say 
much  above  140°F.,  the  oil  will  oxidize  in  time  and  may  produce 
a  carbonaceous  deposit;  for  such  conditions,  the  oil  must  be 
changed  at  sufficiently  frequent  intervals  to  prevent  trouble, 
whereas  ordinarily  the  oil  need  not  be  changed  more  often  than 
every  three  to  six  months. 

Grease  is  often  used,  and  should  be  used,  when  bearings  operate 
in  a  dusty  or  very  humid  atmosphere.  The  grease  must  fill 
the  bearing  cavity  completely,  but  must  not  be  forced  in  so 
tightly  as  to  impede  the  movements  of  the  balls  or  rollers; 
high  speed  bearings  have  been  known  to  develop  abnormal 
heat  due  to  this  cause.  Replenishing  with  grease  should  pre- 
ferably be  done  with  small  quantities  at  a  time;  if  a  big  amount 
of  grease  is  forced  in  by  the  grease  gun  or  grease  cup,  trouble  of  the 
kind  described  is  apt  to  occur. 

When  the  grease  chamber  is  filled  for  the  first  time  the  grease 
may  be  melted  by  gentle  heat  (immersion  in  boiling  water)  and 
poured  into  the  bearing;  but  when  high  melting  point,  fibrous 
greases  are  used,  this  practice  is  not  to  be  recommended. 

The   grease  must  be  as  nearly  neutral  as  possible,  containing 


190  PRACTICE  OF  LUBRICATION 

neither  acid  nor  alkali,  and  it  is  essential  that  during  manufac- 
ture it  has  been  strained  to  remove  all  solid  impurities. 

The  grease  must  not  contain  any  filler,  as  chalk,  gypsum,  or  the 
like,  nor  must  it  contain  an  excessive  amount  of  water;  in  good 
quality  boiled  greases  the  water  content  is  less  than  1  per  cent, 
and  will  not  cause  rusting,  as  in  grease  filled  bearings  the  air 
has  no  access  to  the  surfaces. 

Some  greases  are  quite  free  from  water,  being  simply  petroleum 
jelly  or  mixtures  of  this  material  with  mineral  oil  in  various 
proportions.  The  melting  points  of  such  greases  are  very  low; 
the  melting  points  of  boiled  greases — cup  greases  and  fibrous 
greases — are  higher,  particularly  for  the  latter  type  which  are 
therefore  used  under  conditions  of  high  room  temperatures. 

The  grease  should  be  of  as  soft  a  consistency  as  possible,  say 
No.  1  or  No.  2  consistency  at  the  running  temperature,  so  as  to 
penetrate  and  cover  all  parts  inside  the  bearings.  Many  auto- 
mobile bearings  have  been  ruined  because  too  viscous  greases 
have  been  employed,  which  cannot  possibly  penetrate  to  the 
points  required. 

At  one  time  many  manufacturers  of  ball  and  roller  bearings 
favored  the  use  of  mineral  jelly  greases  because  of  their  freedom 
from  moisture,  but  the  general  experience  with  these  mixtures 
of  mineral  jelly  and  mineral  oil  has  not  been  satisfactory  on 
account  of  their  deficient  lubricating  properties.  For  ball 
bearings  with  flat  races  which  require  hardly  any  lubrication, 
such  greases  have  answered  the  purpose  fairly  well,  but  when 
some  lubricating  power  is  required  boiled  lime  greases,  either 
cup  greases  or  fibrous  greases,  are  much  to  be  preferred. 

For  heavy  duty  roller  bearings  such  greases  should  be  made 
from  a  viscous  mineral  oil  like  Bearing  Oil  No.  5;  whereas  for 
light  duty  roller  bearings  and  for  all  ball  bearings  an  oil  like  Bearing 
Oil  No.  3  is  to  be  recommended. 

Solidified  oils  must  never  be  used  for  ball  or  roller  bearings,  as 
they  are  not  nearly  so  uniform  as  the  boiled  greases;  they  fre- 
quently contain  a  slight  excess  of  alkali  or  acid  in  tiny  pockets 
due  to  the  ingredients  not  being  so  thoroughly  mixed  and  com- 
bined as  is  the  case  in  boiled  greases. 

LUBRICATION  CHART  NO.  3 
FOR  BALL  AND  ROLLER  BEARINGS 

Bearing  Oil  No.  2.1  For  small  and  medium  size  ball  bearings 
and  for  small  roller  bearings  with  little  or  no  end  thrust. 

1  For  Bearing  Oils,  see  page  127. 


BALL  AND  ROLLER  BEARINGS  191 

Bearing  Oil  No.  4.  For  large  ball  bearings  and  for  such  smaller 
ball  bearings  in  which  Bearing  Oil  No.  2  causes  excessive  oil 
spray  or  leakage. 

For  small  or  medium  size  roller  bearings  with  end  thrust. 

For  large  roller  bearings  with  little  or  no  end  thrust. 

Bearing  Oil  No.  6.  For  roller  bearings,  heavily  loaded  and  with 
end  thrust,  or  exposed  to  high  temperatures. 

Cylinder  Oil  No.  2  F.S.M.  (see  Table  No.  19).  For  roller 
bearings  under  extreme  conditions  of  pressure  or  temperature. 

Cup  Grease  No.  1  (made  with  light  oil) .     For  small  ball  bearings. 

Cup  Grease  No.  2  (made  with  light  oil).  For  medium  and 
large  size  ball  bearings  and  for  small  roller  bearings  with  little 
or  no  end  thrust. 

Cup  Grease  No.  2  (made  with  viscous  oil).  For  all  sizes  of 
roller  bearings. 

Fibre  Grease  No.  2  (made  with  viscous  oil).  For  use  in  place 
of  Cup  Greases  No.  1  and  No.  2  when  the  bearings  are  exposed 
to  high  room  temperatures. 


CHAPTER  XIII 
STEAM  TURBINES 

HORIZONTAL  STEAM  TURBINES 

Small  turbines  from  5  H.P.  to  300  H.P.  operate  at  very  high 
speed,  from  3,000  to  30,000  R.P.M.,  and  are  used  for  driving 
exhausters,  exciter  sets,  small  lighting  plants,  high  speed  pumps, 
etc.,  both  ashore  and  on  board  ships. 

Large  stationary  turbines  from  300  to  35,000  H.P.  operate 
at  lower  speeds,  from  750  to  3,600  R.P.M.,  and  are  principally 
used  to  drive  electric  generators  in  electric  power  stations,  in 
collieries,  steelworks,  paper  mills,  textile  mills,  etc. 

Marine  steam  turbines  are  used  for  the  propulsion  of  nearly  all 
warships,  except  submarines  and  some  small  naval  craft.  They 
are  also  used  for  the  propulsion  of  steamers  in  mail  passenger 
service  where  high  speed  is  essential.  Lately,  the  use  of  a  special 
type  of  marine  steam  turbine,  namely  the  geared  turbine,  has 
come  into  great  favor  not  only  for  warships  but  also  for  cargo 
boats. 

Installations  have  been  made  of  from  4,000  to  70,000  H.P. 
in  a  single  ship.  Marine  steam  turbines  are  frequently  con- 
structed with  high  pressure  turbines,  intermediate  pressure  tur- 
bines and  low  pressure  turbines,  but  sometimes  there  are  only 
high  pressure  and  low  pressure  turbines.  It  is  usual  to  have  two, 
three,  or  four  propeller  shafts,  each  shaft  being  driven  by  one  or 
two  turbines.  On  two  of  the  shafts  there  are  reduced  pressure 
astern  turbines  which  are  only  used  for  going  astern.  Generally, 
the  low  pressure  turbines  are  mounted  on  the  same  shafts  as 
the  astern  turbines,  close  together  with  a  common  exhaust. 
Combinations  may  be  made  between  reciprocating  engines  and 
marine  steam  turbines,  the  exhaust  steam  from  the  steam  engines 
being  used  for  operating  the  turbines. 

The  speed  of  marine  turbines  used  in  the  merchant  service 
varies  between  160  and  300  R.P.M.,  whereas  in  naval  practice 
the  speed  may  be  anything  up  to  600  R.P.M.  and  on  certain 
turbines  in  the  United  States  Navy  the  maximum  running  speed 
goes  as  high  as  900  R.P.M. 

Geared  Turbines. — The  geared  type  of  steam  turbine  is  a  re- 
cent development.  It  has  been  used  in  land  installations  but 
particularly  for  marine  services.  Installations  have  been  made 
of  from  4,000  to  20,000  H.P.  on  a  single  shaft.  The  turbine  oper- 

192 


STEAM  TURBINES  193 

ates  at  high  speed  similar  to  the  ordinary  land  steam  turbine,  and 
drives  by  means  of  gearing  the  propeller  shaft  at  low  speed.  The 
result  is  that  the  steam  is  efficiently  utilized  in  the  steam  tur- 
bine and  the  propeller  efficiency  is  also  high,  so  that  the  combined 
efficiency  is  considerably  greater  than  where  steam  turbines  drive 
the  propeller  shafts  direct. 

The  Ljungstrom  Turbine  is  a  special  type  of  geared  turbine 
operating  at  very  high  speed,  say  from  4,000  to  7,000  R.P.M. 
driving  through  gearing  two  electric  generators.  When  used  in 
marine  service  the  electric  current  produced  drives  high  speed 
electric  motors  (say  900  R.P.M.)  coupled  through  gearing  to  the 
propeller  shafts  (operating  at  say  90  R.P.M.). 

Types  of  Turbines. — Parson's  Type  Turbines. — These  tur- 
bines have  a  great,  number  of  revolving  and  stationary  discs,  the 
steam  acting  on  the  blades  more  by  its  pressure  than  by  the 
speed  at  which  it  impinges  on  the  blades.  The  speed  rarely 
exceeds  3,000  R.P.M. 

De  Laval  Type  Turbines. — These  turbines  have  only  one  re- 
volving disc;  the  steam  passes  through  several  nozzles  and  im- 
pinges on  the  blades  with  very  high  velocity,  the  action  being 
similar  to  that  of  a  Pelton  wheel.  The  De  Laval  Turbines  run 
at  a  speed  of  10,000  to  30,000  R.P.M. 

The  Parsons  and  De  Laval  types  of  turbine  represent  fun- 
damentally different  principles  of  operation,  and  all  other  types 
of  turbines  are  adaptations  or  combinations  of  these  two  prin- 
ciples. The  difference  in  design,  however,  affects  only  the 
arrangement  of  the  revolving  and  stationary  discs,  steam  distri- 
bution to  these  discs,  etc.,  and  does  not  greatly  influence  the 
methods  of  lubrication. 

Steam. — According  to  the  steam  used,  turbines  are  classified 
as  follows : 

1.  High  Pressure  Steam  Turbines. 

2.  Exhaust  Steam  Turbines. 

3.  Mixed  Pressure  Steam  Turbines. 

1.  High  pressure   steam  turbines  take  steam  direct  from  the 
boilers  at  160  to  200  Ibs.  pressure  per  square  inch.     The  steam 
after  leaving  the  boilers  is  frequently  superheated. 

2.  Exhaust  steam  turbines  principally  use  the  steam  exhausted 
from  reciprocating  engines,   i.e.,   steam    hammers,   rolling  mill 
engines,  or  colliery  winding  engines.     The  pressure  of  this  steam 
is  only  a  few  pounds  per  square  inch.     Before  entering  the  tur- 
bine the  steam  passes  an  accumulator,  which  causes  a  steady 
flow  of  steam  to  the  turbine.     Exhaust  steam  is  always  very 
moist,  carrying  fine  particles  of  water  in  suspension. 

13 


194  PRACTICE  OF  LUBRICATION 

3.  Mixed  Pressure  Steam  Turbines. — Where  there  is  not  suffi- 
cient exhaust  steam  to  operate  a  turbine  regularly,  or  where  the 
supply  of  exhaust  steam  varies  considerably,  and  at  times  be- 
comes inadequate,  the  requisite  quantities  of  high  pressure  steam 
are  automatically  admitted  to  the  turbine;  hence  the  name 
"  mixed  pressure  steam  turbines." 

Where  exhaust  steam  is  taken  from  large  steam  engines,  it  is 
important  that  the  steam  be  thoroughly  freed  from  cylinder  oil 
and  impurities  before  entering  the  turbine,  as  otherwise  the  tur- 
bine blades  will  be  coated  with  oily  deposit.  The  turbine  blades 
can  be  cleaned  easily  by  injecting  at  regular  intervals,  by  means 
of  a  hand-operated  pump,  from  1  pint  to  1  quart  of  kerosene  per 
week.  When  the  steam  is  very  dirty  or  greasy  a  maximum  amount 
of  1  pint  per  12  hours  should  suffice. 

LUBRICATION 

Owing  to  the  high  speed  at  which  all  turbines  operate,  and  to 
the  fact  that  very  little  wear  may  cause  disastrous  results,  the 
question  of  proper  lubrication  of  the  turbine  bearings  is  of  the 
greatest  importance.  If  the  oil  supply  fails,  even  for  a  very  short 
period,  or  should  the  lubrication  for  other  reasons  become  momen- 
tarily defective,  the  bearing  in  question  will  heat  up  quickly  and 
seizure  will  occur  almost  certainly  before  it  is  possible  to  stop  the 
turbine.  As  a  rule  turbine  bearings  either  operate  at  a  fairly 
normal  temperature,  or  they  are  dangerously  warm;  for  this  rea- 
son every  possible  precaution  should  be  taken  to  ensure  a  never- 
failing  supply  of  oil  of  the  highest  quality  to  each  individual 
bearing,  and  the  bearing  should  be  carefully  designed  with  a  view 
to  giving  the  oil  every  chance  to  distribute  itself  quickly  over  the 
entire  bearing  surfaces.  Turbine  oils  must  be  specially  manu- 
factured to  withstand  the  destructive  action  of  water,  impurities 
and  air  during  continuous  service. 

Lubricating  Systems. — Drop  Feed  Oilers. — In  the  early  days 
of  the  turbine,  the  bearings  were  fitted  with  sight-feed  drop 
oilers,  which  could  be  regulated  to  give  a  certain  number  of  drops 
per  minute,  the  feed  being  entirely  by  gravity.  As,  however,  the 
feed  varied  with  the  height  of  oil  in  the  oil  container,  the  oilers 
needed  constant  attention  in  the  way  of  adjusting  the  needle 
valves  controlling  the  feed,  or  filling  up  of  the  oil  reservoirs. 
Apart  from  this,  the  " drop-feed  method"  soon  showed  its  short- 
comings when  bearings  were  inclined  to  be  troublesome,  which 
was  not  infrequently  the  case,  necessitating  an  increased  oil  feed 
and  extra  close  attention  on  the  part  of  the  attendant. 

The  real  cause  of  the  small  margin  of  safety  was  that  the  fric- 


STEAM  TURBINES  195 

tion  was  high  owing  to  the  high  surface  speed,  and  further  that 
all  the  heat  in  the  bearing  had  only  one  way  of  escape,  namely, 
through  radiation  to  the  engine-room  from  the  outside  of  the 
bearing  housings  and  pedestals.  The  bearings  were  always, 
operating  at  a  temperature  much  above  that  of  the  engine-room, 
partly  due  to  the  frictional  heat  developed  in  the  bearings,  and 
partly  due  to  the  heat  conducted  along  through  the  turbine  shaft. 

Ring  Oiling. — In  modern  turbine  practice  the  "  drop-feed 
method"  has  been  almost  entirely  superseded  by  continuous 
force-feed  oiling  systems,  and  in  the  case  of  some  few  makes  of 
small  turbines  ring  oiling  bearings  have  been  adopted  for  turbines 
below  200  H.P. 

A  more  positive  system  than  the  ordinary  ring-oiling  arrange- 
ment is  illustrated  in  Fig.  72,  the  oil  ring  (1)  having  a  "U" 


FIG.  72. 

section,  and  the  oil  being  continuously  diverted  into  the  bearing 
by  the  stationary  oil  scoop  (2).  If  the  oil  well  contains  a  fair 
quantity  of  oil  the  heat  can  be  readily  conducted  to  the  bearing 
pedestal,  and  radiate  into  the  engine-room  without  the  bearings 
getting  uncomfortably  warm.  Water  cooling  of  the  oil  has  been 
resorted  to  in  some  cases  with  very  good  results:  (a)  in  the  shape 
of  a  cooling  coil  in  each  bearing  pedestal;  (6)  by  casting  the  two 
bearing  halves  with  cavities  for  water  circulation;  or  (c)  by  having 
a  central  oil  cooler  and  an  oil  pump  forcing  the  oil  through  the 
cooler  and  thence  into  the  various  bearing  oil  wells.  The  oil 
overflows  from  each  bearing  back  into  the  tank  from  which  the 
oil  pump  draws  its  supply,  and  circulates  the  oil  afresh.  Using 
ordinary  ring  oiling  bearings  without  water  cooling  is,  of  course, 
cheaper  than  a  forced-feed  circulation  system,  but  does  not  give 


196  PRACTICE  OF  LUBRICATION 

the  same  margin  of  safety.  Care  should  be  taken  that  the  oil  is 
changed  at  intervals  of,  say,  three  months.  If  the  oil  is  of  good 
quality  it  can  be  used  over  again  after  proper  separation  from 
water,  dirt,  and  other  impurities  in  a  steam-heated  settling  tank, 
followed  by  filtration  through  an  efficient  steam-heated  filter. 

Force  Feed  Circulation. — This  system  is  in  general  use  for 
practically  all  turbines  above  200  H.P.  It  is  only  in 
very  rare  cases  that  the  oil  has  been  forced  into  the  bearings  at 
the  points  of  greatest  pressure,  lifting  the  shaft  of  the  rotor 
and  thereby  keeping  it  " floating."  In  order  to  accomplish  that, 
an  oil  pressure  somewhat  higher  than  the  maximum  bearing 
pressure  per  square  inch  is  required.  If  several  bearings  are  fed 
from  the  same  oil  distributing  pipe,  they  must  all  have  approxi- 
mately the  same  load  per  square  inch,  as  otherwise  the  bearing 
with  lower  bearing  pressure  would  rob  the  other  bearings  of  a 
portion  of  their  share  of  the  oil  supply,  the  oil  naturally  taking 
the  way  of  least  resistance. 

The  term  " force  feed"  therefore  generally  means  that  the  oil 
is  kept  in  circulation  by  means  of  a  pump  at  a  pressure  usually 
much  below  the  bearing  pressures.  The  oil  is  introduced  at  the 
top  or  "on"  side  of  the  bearings,  and  wedging  itself  in  between 
the  revolving  shaft  and  the  bearing  surfaces  produces  a  complete 
oil  film  on  which  the  whole  weight  of  the  revolving  part  "  floats." 
If  a  continuous  flow  of  oil  through  the  bearings  is  provided,  the 
oil  carries  away  not  only  the  greater  portion  of  the  frictionalheat, 
but  also  the  heat  conducted  along  through  the  shaft  from  the 
highly  heated  parts  of  the  turbine.  The  combined  loss  from 
friction  and  heat  transmission  into  the  bearings  is  estimated  at 
about  Y%  per  cent,  of  the  rated  horse  power  of  the  turbine. 

The  Oil  Cooler. — It  therefore  becomes  necessary  to  cool  the 
return  oil  frorri  the  bearings,  and  it  cannot  be  too  much  empha- 
sized that  an  efficient,  well  designed  oil  cooler  of  ample  capacity 
is  one  of  the  best  investments  that  can  be  made  in  a  turbine 
plant,  and  is  an  excellent  insurance  against  lubrication  troubles. 
There  is  a  variety  of  designs  of  oil  coolers.  In  the  early  days  they 
were  often  " built  in"  in  the  bed-plate.  This  practice  seems  now 
to  be  practically  abandoned;  because  of  the  proximity  of  cold 
water  and  hot  oil,  extra  stresses  are  set  up  in  the  turbine  bed- 
plate, due  to  the  unequal  expansion  of  the  various  parts,  and  a 
cracked  bed-plate  has  occasionally  been  the  result. 

Another  reason  for  building  the  oil  cooler  separate  from  the  tur- 
bine is  the  vibration  which  tends  to  disturb  joints,  etc.  One 
curious  result  of  heavy  vibration  was  the  wearing  through  of  a 
cooling  coil  rubbing  against  the  bottom  of  the  oil  cooler;  it  was 


STEAM  TURBINES  197 

finally  perforated  and  the  water  leaking  into  the  oil  caused  a 
lot  of  trouble.  When  a  new  coil  was  fitted  it  was  raised  above 
the  bottom,  and  had  small  "feet"  clamped  on  to  the  coils  at 
intervals.  This  successfully  overcame  the  trouble. 

Oil  coolers  should  be  designed  with  a  view  to  facilitating  in- 
spection and  cleaning  of  the  tubes,  internally  as  well  as  externally, 
and  the  water  spaces.  The  oil  cooler  should  always  have  doors 
for  inspection,  large  enough  so  that  the  tubes  can  be  cleaned  on 
the  outside.  The  tubes  should  be  solid  drawn,  seamless,  with 
no  unnecessary  connections,  which  might  cause  leakage;  fre- 
quently, they  are  so  arranged  that  they  can  be  withdrawn  as  a 
whole  for  inspection  and  cleaning. 

In  the  earlier  type  of  coolers  the  tubes  were  usually  of  the 
"U"  type,  but  most  modern  coolers  have  straight  tubes,  which 
are  easier  to  clean.  The  flow  of  oil  and  water  through  the  cooler 
should  always  be  in  opposite  directions,  so  that  the  oil  in  passing 
through  meets  colder  and  colder  water;  in  this  way  the  best 
cooling  effect  is  obtained.  In  most  coolers  the  oil  is  inside  the 
tubes. 

It  is  highly  desirable  that  the  pressure  of  the  oil  in  passing 
through  the  cooler  should  at  all  points  be  higher  than  the  water 
pressure,  so  that  should  any  leakage  occur  it  will  be  of  oil  into 
water;  otherwise  it  will  mean  water  leaking  into  the  oil,  which 
must  be  avoided  for  reasons  given  later  on. 

The  capacity  which  hot  oil  in  particular  possesses  of  percolating 
through  the  most  minute  pores  or  leaks  is  remarkable,  and  leakage 
may  occur  under  running  conditions,  even  if  the  cooler  has  been 
tested  cold  and  found  perfectly  tight  under  great  pressure.  When 
testing  an  oil  cooler  for  leakage  it  should,  therefore,  always  be 
tested  "hot." 

The  cooling  coils  sometimes  get  badly  corroded,  when  acidy 
water  is  used,  and  corrosion  nearly  always  attacks  certain 
"spots"  in  the  tubes,  particularly  if  they  are  made  of  brass. 
It  looks  as  if  local  galvanic  currents  may  often  have  something 
to  do  with  heavy  corrosion,  caused  by  inequalities  in  the  com- 
position of  the  tube  metal  and  due  to  the  presence  of  small  grains 
of  different  metals  close  together — copper,  zinc,  etc.  To  pre- 
vent corrosion  in  oil  coolers  employing  sea  water  an  iron  rod 
fixed  from  end  to  end  of  the  cooler  has  proved  effective;  the 
rod  is  often  eaten  away  by  galvanic  action  in  a  single  voyage. 

The  cooling  water  should  preferably  be  circulated  through  the 
cooler  by  means  of  a  circulating  pump  and  at  a  low  pressure, 
which  falls  to  nil  when  the  turbine  stops  running.  If  the  cooling 
water  is  led  to  the  cooler  by  gravitation  alone,  trouble  may  arise 


198  PRACTICE  OF  LUBRICATION 

from  one  of  the  pipes  or  passages  being  choked  up,  the  ordinary 
flow  and  pressure  of  the  water  being  unable  to  clear  away  the  ob- 
struction. Cases  have  been  known  where  turbine  bearings  have 
seized  because  of  such  obstructions  in  the  cooling  water  inlet 
pipe,  the  oil  temperature  rising  rapidly,  and  the  oil  consequently 
losing  its  lubricating  power.  Had  a  circulating  pump  been 
used  the  obstruction  in  the  pipe  would  probably  not  have  formed 
at  all  or  would,  at  any  rate,  have  been  cleared  away  in  time,  as 
because  of  the  extra  resistance  the  pump  would  automatically 
deliver  the  cooling  water  at  an  increased  pressure.  The  cooling 
water  outlet  from  the  cooler  should  have  a  free  overflow,  which 
will  ensure  a  low  water  pressure.  The  efficiency  of  the  oil  cooler 
is  greatly  affected  by  dirty  cooling  water;  cases  have  been  known 
where  greasy,  muddy  river  water — caused  by  dirty  discharges 
from  works  higher  up  the  river  or  due  to  heavy  rainfall — used  as 
cooling  water  has  deposited  sufficient  slime  and  dirt  to  increase 
the  turbine  oil  temperature  at  the  rate  of  1°F.  per  day. 

The  oil  cooler  has  its  best  place  in  the  circulation  system  after 
the  oil  pump,  not  before,  as  in  the  latter  case  the  oil  is  sucked 
through  the  cooler,  and  any  leakage  would  be  of  water  into  oil. 

Thermometer  pockets  should  be  fitted  in  the  inlet  and  outlet 
oil  pipes,  also  in  the  water  inlet  and  outlet  to  the  oil  cooler,  as  by 
temperature  records  taken,  say,  every 'hour  it  will  at  once  be 
discovered  if  there  is  anything  wrong  with  the  cooler  or  with -the 
oil  in  circulation.  The  water,  if  not  clean,  may  have  thrown  down 
muddy  deposits  on  the  tubes,  or  the  tubes  may  have  been  coated 
on  the  "  oil "  side  with  deposits  from  the  oil  system.  In  any  case, 
the  temperature  records  will  at  once  indicate  whether  trouble  is 
approaching,  and  a  close  investigation  in  good  time  will  locate 
the  cause  and  point  out  the  remedy. 

Shutting  off  the  cooling  water  supply  is  the  last  operation  when 
stopping  a  turbine,  but  the  oiling  should  be  continued  until  the 
turbine  has  come  to  a  standstill. 

In  order  to  calculate  the  amount  of  heat  carried  away  by  the 
cooling  water,  it  is  necessary  to  know  the  quantity  of  cooling 
water  going  through  the  cooler  per  minute.  This  weight  in 
pounds  multiplied  by  the  difference  in  temperature  between  the 
inlet  and  outlet  water  gives  the  total  number  of  British  Thermal 
Units  per  minute.  Where  it  is  not  possible  to  measure  the  quan- 
tity of  cooling  water,  and  where  the  quantity  of  oil  passing 
through  the  cooler  per  minute  is  known,  the  following  calculation 
can  be  made,  to  get  at  the  heat  loss  of  the  oil  in  going  through  the 
cooler.  Multiplying  the  weight  of  oil  in  pounds  per  minute  by 
the  fall  in  temperature  in  going  through  the  cooler  and  by  0.5 — 


STEAM  TURBINES  199 

which  is  approximately  the  specific  heat  of  turbine  oil — gives  the 
number  of  B.Th.U.'s  carried  away  per  minute. 

The  tubes  used  in  oil  coolers  vary  from  %  inch  to  %  inch  in 
diameter  internally.  As  to  the  desirable  size  of  the  cooler  tubes, 
the  cooling  capacity  per  square  foot  of  surface  is  greater  for  the 
smaller  tubes,  as  the  volume  of  oil  in  the  tubes  decreases  with  the 
square  of  the  bore,  while  the  cooling  surface  only  decreases  in 
direct  proportion  to  the  outside  diameter.  If  an  oil  cooler  is 
found  to  be  too  small  in  capacity,  it  is  not  of  much  use  to  in- 
crease the  flow  of  cooling  water  through  the  cooler;  it  will,  of 
course,  make  some  difference,  but  if  the  cooling  water  is  taken 
from  the  coldest  available  supply,  and  if  the  oil  does  not  get 
cooled  sufficiently,  the  only  remedy  is  to  increase  the  capacity 
of  the  cooler  by  adding  more  " surface." 

In  some  installations  where  the  oil  is  inside  the  tubes*an*im- 
provement  has  been  made  by  fitting  twisted  strips — of  the  same 
material  as  the  tubes — inside  the  tubes  in  order  to  disturb  the 
oil  as  much  as  possible;  it  is  obvious  that  as  long  as  the  flow  of 
oil  is  only  1.0  ft.  to  2.0  ft.  per  second,  which  represents  normal 
practice,  the  oil  ordinarily  shoots  through  the  tubes  without  being 
"  broken  up,"  and  a  layer  of  cold  oil  on  the  inside  of  the  tubes 
makes  the  cooling  of  the  oil  in  the  centre  rather  inefficient.  The 
value  of  inserting  the  twisted  strips — retarders — will  easily  be 
understood.  The  total  cooling  surface  of  the  oil  cooler  in  square 
feet  may  be  taken  as  two  to  three  times  the  quantity  of  oil  in 
gallons  circulated  per  minute;  the  lower  figure  must  only  be 
used  with  very  small  bore  tubes  or  where  the  tubes  are  fitted  with 
retarders. 

Experiments  carried  out  by  Mr.  Boella  ("  Engineering,"  March 
2d,  1917)  indicate  that  the  heat  transmission  per  hour  through 
ordinary  cooler  tubes  ranges  from  70-200  B.Th.U.'s  per  sq.  ft.  per 
°F.  or  from  25-73  calories  per  sq.  m.  per  °C.  difference  in  tempera- 
ture, whereas  with  flattened  cooler  tubes,  the  flow  of  oil  is  lami- 
nated, giving  an  increased  heat  transmission  of  370-490  B.Th.U.'s 
per  sq.  ft.  per  °F.  or  136-180  calories  per  sq.  m.  per  °C.  These 
results  indicate  great  possibilities  for  improving  existing  types 
of  oil  coolers. 

The  Oil  Pump. — In  some  of  the  earlier  turbines  a  reciprocating 
pump  was  employed,  but  very  soon  the  change  was  made  to 
valveless  designs.  Later  the  development  has  been  in  the  direc- 
tion of  rotary,  toothed  wheel  pumps  driven  by  worm  or  skew 
gearing  off  the  main  turbine  shafts.  The  toothed  wheel  pump 
is  more  positive  in  action  than  the  valveless  " sliding  vane" 
type  of  pump;  also  there  is  less  chance  of  the  toothed  wheel 


200  PRACTICE  OF  LUBRICATION 

pump  being  accidentally  choked  with  rusty  scale,  dirt,  etc.,  as 
the  oil  has  a  more  effective  washing  action  in  passing  through  the 
pump.  On  the  other  hand,  the  toothed  wheel  pump  has  the 
disadvantage  that  the  oil  is  " churned"  more  vigorously  and  may 
consequently  suffer  more  when  water  happens  to  be  present. 

The  oil  strainer  consists  of  copper  or  brass  gauze,  supported  by 
a  perforated  cylinder,  which  it  covers.  This  cylinder  should  be 
of  the  same  metal  as  the  gauze,  as  otherwise  galvanic  action  comes 
into  force  and  destroys  the  strainer  by  pitting  and  corrosion.  The 
oil  strainer  should  be  situated  in  a  position  well  clear  of  the  bottom 
of  the  oil  tank,  say  4  in.  to  6  in.,  to  allow  the  water  that  al- 
most invariably  leaks  into  the  oil  to  separate  out,  so  that  it  can 
be  drained  away  through  a  drain  or  sludge-cock  of  ample  dimen- 
sions, not  less  than  \Y%  in.  bore.  The  need  for  such  a  big  bore  is 
on  account  of  the  sludge,  which  may  be  formed  in  the  oil,  and 
which  will  not  drain  out  through  a  small  opening.  If  the 
strainer  is  placed  close  to  the  bottom  of  the  tank,  water  is  sucked 
into  the  pump  first  of  all  and  is  not  given  a  chance  to  separate 
out  from  the  oil.  Care  should  be  taken  to  have  sufficient  oil 
above  the  top  of  the  strainer  so  that  no  air  can  be  drawn  in  with 
the  oil,  as  "aeration"  of  the  hot  oil  has  an  oxidizing  effect  and 
may  cause  decomposition  of  the  oil,  if  the  temperature  is  high. 

In  large  installations  the  oil  pumps  are  nearly  always  operated 
separately  from  the  turbine,  either  electrically  or  by  steam;  the 
pumps  are  started  up  before  the  turbine  and  kept  in  operation 
until  the  turbine  has  come  to  a  standstill.  In  smaller  installa- 
tions, where  the  oil  pump  is  an  integral  part  of  the  turbine,  the 
pump  will  not  supply  a  sufficient  quantity  of  oil  until  a  certain 
speed  has  been  reached;  it  therefore  becomes  necessary  to  have 
an  auxiliary  oil  supply  that  works  independently  of  the  turbine- 
driven  oil  pump.  This  auxiliary  supply  is  usually  a  hand  pump, 
with  which  the  bearings  can  be  flushed  before  and  during  the 
starting  up  of  the  turbine;  in  larger  installations  a  hand-operated 
pump  becomes  inadequate,  and  the  auxiliary  oil  pump  is  driven 
by  an  electric  motor  or  by  steam.  It  cannot  be  too  strongly  em- 
phasized that  the  bearings  should  be  continuously  flushed  until 
the  speed  of  the  turbine  is  about  20  to  25  per  cent,  of  the  normal, 
this  should  also  be  done  when  in  stopping  the  turbine  the  speed 
has  fallen  to  the  speed  just  mentioned.  By  watching  the  pres- 
sure gauge  attached  to  the  main  circulating  system,  the  attendant 
can  always  be  guided  as  to  the  time  when  it  will  be  safe  to  discon- 
tinue the  auxiliary  oil  supply. 

The  oil  pump  should  be  designed  to  give  a  supply  of  oil  at  the 
pressure  required,  equalling  0.05  to  0.15  gallon  per  minute  per 
square  inch  of  total  projected  bearing  surface. 


STEAM  TURBINES  201 

The  strainer  on  the  suction  side  of  the  oil  pump  should  have 
an  area  in  square  inches  equalling  from  four  to  six  times  the  number 
of  gallons  of  oil  circulated  per  minute. 

The  quantity  of  oil  present  in  the  circulation  system  should  be 
from  0.15  gallon  per  kilowatt  for  smaller  turbines  to  OJO  gallon 
per  kilowatt  for  the  largest  units,  but  the  minimum  amount  of 
oil  in  any  turbine  should  preferably  be  120  gallons.  | 

Oil  Pressure  and  Circulation  Systems. — On  leaving  the  oil 
cooler  the  oil  goes  generally  to  the  main  oil  distributing  pipe, 
which  runs  along  the  turbine  bed  and  from  which  branch  pipes 
lead  it  into  the  various  bearings.  It  is  forced  into  the  main  oil 
pipe  under  a  certain  pressure  which  is  regulated  by  means  of  a 
spring-loaded  relief  valve;  this  valve  can  be  regulated  to  give 
any  desired  pressure  within  certain  limits,  and  the  surplus  oil  is 
allowed  to  discharge  back  into  the  suction  oil  tank. 

Another  way  of  maintaining  a  certain  oil  pressure  is  to  force 
the  oil  up  into  an  elevated  tank,  from  which  it  is  led  through  a 
main  pipe  down  to  the  turbine  and  then  distributed  in  the  ordinary 
way.  This  system  has  the  advantage  that,  should  the  oil  pump 
fail  for  some  reason  or  other,  the  top  tank  will  continue  the  supply 
for  a  sufficient  length  of  time  to  allow  the  turbine  to  be  shut  down 
before  any  damage  is  done.  Unless  the  top  tank  is  hermetically 
closed,  this  system  does  not  allow  of  any  alteration  in  the  oil 
pressure,  as  the  pressure  will  be  dependent  entirely  upon  the 
height  of  the  oil  level  in  the  top  tank  above  the  level  of  the  turbine 
bearings.  The  top  tank  should  be  fitted  with  an  overflow  pipe 
to  carry  surplus  oil  down  into  the  return  oil  tank.  It  should 
also  have  a  drain  or  sludge  cock  of  at  least  l^-inch  bore  and  a 
drain  pipe. 

The  return  oil  tank  must  be  of  sufficient  capacity  to  take  the 
whole  of  the  oil  in  the  system,  in  case  during  a  standstill  the  whole 
of  the  oil  in  the  top  tank  should  be  allowed  to  run  down  into  the 
bottom  tank. 

" Sight  feeds"  are  sometimes  fitted  in  the  inlet  branch  pipes 
to  the  bearings,  their  position  being  between  the  bearings  and 
regulating  cocks  fitted  in  the  inlet  pipes.  It  is,  however,  difficult 
to  keep  them  clean.  If  the  oil  drops  through  the  sight  feeds  it 
has  a  tendency  to  take  the  air  away,  and  the  sight  feeds  fill  up 
with  oil.  The  same  unsatisfactory  results  is  generally  experi- 
enced where  the  sight  feeds  are  filled  with  water  and  the  stream 
of  oil  is  made  to  rise  through  the  water;  the  oil  carries  the  water 
away,  and  the  glasses  fill  up  with  oil. 

It  is,  of  course,  very  desirable  to  have  efficient  sight  feeds,  but 
it  is  preferable  to  fit  them  in  the  return  oil  pipes  from  each 


202  PRACTICE  OF  LUBRICATION 

bearing.  Care  should  be  taken  that  the  outlets  have  ample 
openings  to  allow  of  the  oil  running  through  freely,  otherwise  it 
cannot  escape  from  the  bearings  quickly  enough,  and  overflows 
through  the  bearing  ends.  Some  makers  just  fit  a  small  test 
cock  on  each  bearing,  which  if  opened  shows  whether  the  inlet 
pipe  is  supplied  with  pressure  oil  or  otherwise,  but,  of  course,  this 
does  not  give  any  idea  as  to  how  much  oil  goes  through  each 
bearing. 

In  plants  with  a  top  oil  tank,  distributing  the  oil  by  gravity,  the 
oil  pressure  is  a  fixed  figure,  but  where  the  oil  is  distributed 
direct  from  the  oil  pump,  the  maximum  oil  pressure  that  can  be 
obtained  depends  upon  the  capacity  of  the  pump  and  the  resist- 
ance offered  to  the  oil  in  its  passage  through  the  oil  pipes  and 
the  bearings.  The  warmer  the  oil — or  the  thinner  .the  oil  in  use — 
the  lower  will  be  the  maximum  oil  pressure  obtainable,  as  the 
thinner  oil  passes  more  easily  through  the  bearings,  and  leaks 
more  freely  in  the  case  of  a  rotary  oil  pump,  i.e.,  the  pump  dis- 
charges less  oil  per  revolution. 

A  lowering  of  the  oil  pressure  of  a  dangerous  nature  may  take 
place  when  unsuitable  oil  gets  very  thick  and  sludgy,  due  to 
emulsification  with  water,  particularly  if  the  pump  strainers  are 
covered  with  sludge.  Under  these  conditions  a  vacuum  is 
formed  in  the  pump,  it  " slips"  and  does  not  operate  with  its 
full  capacity;  hence  the  oil  pressure  falls,  sometimes  with  only 
short  warning,  and  may  cause  disastrous  results.  When  a 
turbine  starts  up  "cold,"  the  oil  pressure  is  usually  high,  even  if 
the  relief  valve  is  fully  open;  as  the  oil  warms  up,  the  pressure 
falls,  but  should  not  fall  more  than  can  be  met  by  partly  closing 
the  relief  valve  when  the  running  temperature  has  been  reached, 
thus  leaving  a  margin  over  and  above  the  minimum  pressure 
required  to  operate  the  governor  gear. 

The  cooling  water  service  should  not  be  put  on  until  the  oil 
in  circulation  has  warmed  up  to  within  20°F.  of  its  normal 
temperature. 

As  regards  the  oil  pressure  required  for  distributing  the  oil 
with  certainty  to  the  bearings,  a  few  pounds  per  square  inch  will 
be  found  adequate  to  give  a  satisfactory  supply,  say  from  5  Ib. 
to  15  Ib.  per  square  inch. 

In  many  modern  designs  of  turbines  the  oil  is  made  use  of  in 
several  other  ways,  the  principal  one  being  in  connection  with  the 
operation  of  the  governor  gear.  It  is  beyond  the  scope  of  this 
book  to  go  into  the  various  designs  of  oil-worked  governor  gears, 
but  the  author  would  like  to  emphasize  the  necessity  of  using 
good  quality  oil  and  keeping  it  in  first-class  condition;  otherwise 


STEAM  TURBINES 


203 


the  result  may  easily  be  sluggish  and  unsatisfactory  govern- 
ing, as  some  of  the  clearances  are  exceedingly  fine.  One  point 
worth  mentioning  is  that,  where  a  vertical  spindle  operates  the 
steam  throttle  valve  below,  the  oil-worked  piston  being  above 
(see  Fig.  73),  the  stuffing  box  of  the  oil  cylinder  invariably  leaks 
slightly.  If  this  oil  is  allowed  to  trickle  down  on  top  of  the  throt- 
tle valve  cover  it  will  smoke  and  "bake  on"  in  the  form  of  a 
carbon  deposit,  particularly  when  superheated  steam  is  used;  this 
is  rather  objectionable  and  may  easily  be  prevented  by  fixing  a 
cup  on  the  spindle  and  a  drain  to  carry  oil  away  outside  the 
throttle  valve,  as  shown. 


1  Pressure  Oil  Inlet 

2  Pressure  Oil  Outlet 

3  Springloaded  Piston 

4  Throttle  Valve  Spindle     O 

5  Oil  Drain 


FIG.   73. — Turbine  throttle  valve. 

The  principle  of  operation  of  oil-worked  governors  embodies 
a  pilot  valve,  which  is  moved  by  the  governor,  and  which  when 
moved  allows  pressure  oil  to  flow  into  an  oil  relay  cylinder,  there- 
by causing  a  spring-loaded  piston  to  rise  or  fall  in  this  cylinder, 
according  to  whether  the  oil  is  introduced  above  or  below  the 
piston,  or,  if  only  acting  on  the  underside,  according  to  whether 
the  oil  is  admitted  or  not.  The  piston,  moving  with  great  force, 
acts  directly  on  the  main  steam  valve.  When  the  oil  supply  to 
the  governor  is  taken  from  the  main  oil  circulation  system,  a 
failure  of  this  oil  supply  will  cause  the  relay  piston  to  descend 
and  shut  off  the  steam  supply  operating  the  turbine.  The  tur- 


204  PRACTICE  OF  LUBRICATION 

bine  cannot  start  until  a  sufficient  oil  pressure  has  been  obtained 
in  the  oil  supply  system,  and  consequently  any  damage  to  the 
bearings  due  to  insufficient  pump  pressure  is  thus  obviated. 

The  oil  pressure  required  by  the  governor  gear  is  high,  from 
25  Ib.  to  60  Ib.  per  square  inch,  in  accordance  with  the  require- 
ments of  the  various  designs. 

Several  makers  fit  two  oil  pumps,  one  pump  delivering  small 
quantities  of  oil  under  great  pressure  for  the  governor  gear,  the 
other  pump  delivering  large  quantities  of  oil  at  low  pressure  for 
lubricating  the  bearings. 

Oil  Pipes. — The  distributing  oil  pipes  should  be  of  ample  pro- 
portions, with  as  few  bends  as  possible.  The  branch  pipes  lead- 
ing to  the  bearings  should  not  join  the  main  oil  pipe  at  right 
angles,  but  preferably  at  an  angle  not  more  than  30°,  with  a  view 
to  decreasing  the  loss  in  oil  pressure  due  to  fluid  friction  and 
resistance. 

As  regards  the  return  oil  pipes  from  the  different  bearings, 
these  should  be  of  ample  proportions,  so  that  the  maximum 
quantity  of  oil  from  each  bearing  may  return  comfortably; 
otherwise  the  oil  may  overflow  through  the  bearing  ends  and 
cause  unsightly  waste  of  oil,  with  a  possibility  in  the  case  of  turbo- 
generators of  the  oil  being  drawn  over  into  the  generator  and 
spoiling  the  insulation.  The  branch  pipes  should  meet  the  main 
return  pipe  at  an  angle  of  -not  more  than  30°,  and  in  case  of 
" sight  feeds"  in  the  branch  pipes,  these  should  be  designed  so 
that  air  does  not  get  churned  with  the  oil  causing  aeration.  At 
no  place  must  the  flow  of  oil  be  broken  up  or  violently  disturbed. 

During  late  years  most  turbine  makers  have  made  the  oil 
pipes  of  steel  or  wrought  iron  instead  of  copper,  which  originally 
was  used  exclusively.  This  has  been  done  largely  in  view  of 
lower  first  costs,  but  it  is  very  questionable  whether  this  step  is 
an  altogether  wise  one.  The  oil  is  nearly  always  charged  with 
finely  divided  globules  of  air  and  water,  and  through  the  con- 
tinued use  the  oil  always  becomes  slightly  acidy.  These  features 
combined  cause  corrosion  of  the  iron  or  steel  pipes  in  a  much 
higher  degree  than  when  the  pipes  are  made  of  copper — in  fact, 
copper  is  hardly  affected.  (See  page  221  and  Example,  page  226.) 

Bearings. — The  load  on  the  main  bearings  of  a  turbine  is 
mainly  due  to  the  weights  of  the  rotor,  shaft  and  generator,  if 
any.  The  pressure  is  therefore  the  same,  whether  the  turbine  is 
under  load  or  otherwise,  and  is  never  relieved,  as  is  the  case  with 
the  principal  bearings  of  reciprocating  engines.  It  is  conse- 
quently of  the  very  greatest  importance  to  design  the  bearings 
with  a  view  to  quick  distribution  of  the  oil,  particularly  in  the 


STEAM  TURBINES 


205 


case  of  marine  turbines,  where  greater  pressures  per  square  inch 
are  carried  in  connection  with  lower  surface  speed.  A  high 
surface  speed  draws  the  oil  in  between  shaft  and  bearing  and 
makes  it  possible,  and  desirable,  to  use  free  flowing  oils.  On  the 
other  hand,  the  lower  surface  speed  and  higher  bearing  pressures 
met  with  in  marine  practice  necessitate  the  use  of  heavier  bodied 
oils  and  may  even  make  careful  oil  grooving  desirable. 

With  high  surface  speed,  oil  grooves  should  be  dispensed 
with  altogether,  being  distinctly  detrimental,  as  they  reduce 
the  area  of  the  bearing  surface. 

The  following  figures  represent  current  turbine  practice: 
Bearing  pressures  40  Ib.  to  85  Ib.  per  square  inch;  surface  speed 
25  ft.  to  80  ft.  per  second;  product  of  pressure  per  square  inch  by 
speed  per  second,  1500  to  5000,  the  higher  figures  being  for  high 
speed  land  turbines,  while  the  lower  figures  represent  marine 
practice.  As  an  example,  the  following  particulars,  having 
reference  to  the  turbine  ship  "Lusitania,"  which  has  two  high- 
pressure  and  two  low-pressure  ahead  turbines  and  two  astern 
turbines,  are  given: 


Effective 
projected 
area,  in. 

P 

Bearing 
pressure, 
Ib.  per  sq.  in. 

V 
Surface 
speed, 
ft.  per  sec. 

P  X  V 

R.P.M. 

H.P.  bearings.  .  . 

27^X44% 

80 

22K 

1800 

190 

L.P.  bearings.  .  . 

33>6X56H 

72 

.  27K 

1980 

190 

"Astern"  bear- 

ings   

24«X34?i 

83 

20 

1660 

190 

The  bearings  are  of  cast  iron,  lined  with  white  metal  on  their 
running  surfaces.  At  the  centre  of  each  bearing  is  fitted  a  safety 
strip  of  "Ajax"  bronze  J^oo  m-  below  the  surface  of  the  white 
metal.  Should  the  white  metal  accidentally  get  heated  so  that 
it  runs,  the  rotor  will  be  supported  by  the  bronze  strip  and  thus 
be  prevented  from  dropping  sufficiently  to  injure  the  blading  by 
rubbing  against  the  interior  of  the  rotor  casing.  The  •bottom 
halves  of  the  bearings  are  cooled  by  water  circulation.  Fig. 
74  illustrates  one  of  the  main  bearings  of  a  large  slow  speed  marine 
turbine.  Note  the  oil  drains  at  both  ends  and  the  oil  throwers 
which  prevent  the  oil  that  creeps  beyond  the  drains  from  getting 
outside  the  bearings.  The  outer  wall  of  the  bearing  is  spherical, 
working  in  a  dished  pedestal  in  order  to  ensure  equal  pressure 
over  the  entire  bearing  surface,  notwithstanding  any  slight 
deflection  in  the  shaft. 

The  oil  enters  the  bearing  recesses  (straight  grooves)  which 


206 


PRACTICE  OF  LUBRICATION 


distribute  the  oil  assisted  by  the  curved  oil  grooves;  the  oil  grooves 
are  not  extended  to  the  edge  of  the  bearing,  but  leave  a  strip  of 
white  metal  intact  in  order  to  keep  up  the  oil  pressure  and  pre- 
vent the  oil  from  getting  away  before  it  has  done  its  duty. 

As  all  the  pressure  is  downward,  the  top  halves  of  the  main 
bearings  carry  no  load,  but  they  must  nevertheless  be  a  good  fit  in 
relation  to  the  lower  halves,  and  in  relation  to  the  shaft  at  both 
ends,  in  order  to  prevent  the  oil  from  escaping  too  freely.  Apart 
from  the  outer  ends — where  the  clearance  may  be  made  0.01  in. — 
the  top  halves  do  not  need  to  touch  the  shaft  in  the  centre  por- 
tion of  the  bearing,  so  that  a  greater  clearance  is  here  allowed. 
Where  the  oil  enters  the  bearing,  the  bottom  half  should  always 
have  a  recess  with  the  distributing  edge  well  rounded  or  "  cham- 
fered," so  that  the  oil  may  quickly,  and  as  easily  as  possible, 
wedge  itself  in  between  the  shaft  and  the  bearing. 


FIG.  74. — Marine  turbine  bearing. 

In  the  case  of  bearings  with  water  cooling  of  the  top  halves  as 
well  as  the  bottom  halves,  it  is  better  to  make  the  water  con- 
nection between  the  two  halves  outside  the  bearings  rather  than 
risk  leakage  of  water  into  the  oil,  which  easily  happens  when  the 
joint  is  inside  the  bearing,  out  of  sight.  Water  cooling  the  top 
halves-  is,  however,  rarely  used,  and  owing  to  possible  annoy- 
ance with  water  cooled  bearings  caused  by  leaky  joints  or  porous 
bearing  metal,  the  tendency  is  nowadays  to  go  away  from  water- 
cooled  bearings  and  depend  entirely  upon  a  well-designed  cooler 
of  ample  capacity. 

In  some  cases  turbine  bearings  have  been  designed  as  oil- 
cooled  bearings,  the  oil  before  entering  the  frictional  surfaces 
first  passing  round  the  outer  surfaces  of  the  bearing  shells. 
The  result  is  that  the  bearings  are  kept  at  a  uniform  temperature 
throughout,  and  that  the  oil  removes  a  little  more  heat  than  it 


STEAM  TURBINES  207 

would  have  done  had  it  been  passed  direct  into  the  frictional  sur- 
faces. 

Should  a  bearing  give  trouble  it  generally  gives  no  warning; 
the  oil  evaporates  and  white  fumes  ooze  out  from  one  or  both 
ends.  The  turbine  should  be  stopped  at  once,  as  the  white 
metal  with  all  certainty  has  commenced  to  run  and  will  want 
renewing  before  the  turbine  can  be  put  under  load  again.  Grit 
or  dirt  may  have  been  the  cause.  Failure  of  the  oil  supply,  if 
due  to  the  oil  pump  pumping  an  insufficient  amount  of  oil, 
will  show  up  in  decreased  oil  pressure  and  should  be  noticed  by 
the  attendant.  Choking  up  of  one  of  the  oil  distributing  pipes  to 
a  particular  bearing  might  be  noticed  in  time,  if  the  bearings  are 
fitted  with  sight  feed  attachments. 

Whenever  a  bearing  cap  has  been  adjusted,  the  turbine  should 
not  be  put  on  full  speed  until  one  is  fully  assured  that  the  bearing 
does  not  pinch  the  shaft. 

The  amount  of  oil  circulated  per  minute  varies  according  to 
the  oil  pressure  required  and  to  the  size  of  the  bearings.  Current 
practice  is  to  circulate  the  oil  at  the  rate  of  0.05  to  0.15  gallon 
per  minute  per  square  inch  of  total  bearing  surface,  as  mentioned 
under  the  heading  "Oil  Pump."  In  the  case  of  slow  speed 
marine  turbines,  a  supply  of  0.02  gallons  per  minute  per  square 
inch  will  be  found  adequate.  This  lower  rate  of  feed  emphasizes, 
however,  the  desirability  in  the  case  of  marine  turbines  of  having 
oil  sight  feeds  in  the  return  pipes  from  each  individual  bearing 
to  make  sure  that  each  bearing  gets  its  proper  share. 

Turbine  Thrust  Bearings. — Where  greater  or  smaller  end 
pressure  has  to  be  taken  up,  due  either  to  the  design  of  the  tur- 
bine itself  or  to  propeller  thrust,  the  thrust  bearing  becomes  an 
important  feature  of  the  turbine. 

Thrust  blocks  for  marine  turbines  are  usually  of  cast  iron,  with 
a  steel  bush  for  holding  the  thrust  rings.  The  top  portion  of  the 
thrust  block  generally  takes  the  steam  thrust  and  the  lower  por- 
tion the  propeller  thrust.  The  block  is  fitted  on  a  sole  plate  of 
its  own  and  can  be  moved  in  a  fore-and-aft  direction;  also  the 
upper  portion  can  be  moved  relatively  to  the  lower  portion  in 
order  to  adjust  the  clearances  of  fore-and-aft  play,  which  may  be 
made  about  0.01  of  an  inch.  The  thrust  rings  may  be  made  of 
gun-metal  with  white  metal  facings  on  the  rubbing  surface. 

It  is  evident  that  when  the  thrust  block  is  supplied  with  oil 
under  pressure  from  the  outer  edges  of  the  thrust  rings,  the  oil 
has  to  go  against  the  action  of  the  centrifugal  force,  and  when  it  is 
between  the  rubbing  surfaces  the  tendency  is  to  squeeze  it  out  all 
the  time;  whereas  in  the  main  bearings  of  the  turbine  the  revolv- 


208  PRACTICE  OF  LUBRICATION 

ing  shaft  draws  the  oil  in  between  the  rubbing  surfaces,  feeding 
the  oil  towards  the  place  where  it  is  needed.  An  increased  oil 
pressure  does  not  help  the  oil  in  the  case  of  a  thrust  block;  the 
oil  has  only  its  natural  clinging  property — oiliness — to  depend 
upon  for  getting  to  the  place  where  it  is  required.  • 

Thrust  blocks  in  steam  engine  propelled  ships  are  lubricated  by 
means  of  oils  heavily  compounded  with  vegetable  oils.  The 
reason  is  that  such  oils,  properly  manufactured,  have  very  great 
clinging  properties,  so  that  they  are  able  to  get  in  between  the 
rubbing  surfaces  better  and  more  easily  than  pure  mineral  oils. 

In  forced  lubricated  thrust  blocks  in  connection  with  marine 
turbines  trie  oil  is  taken  from,  the  main  circulation  system,  as  it 
would  be  cumbersome  to  make  a  separate  oiling  system  for  the 
thrust  blocks.  But  oils  used  for  forced  lubrication  must  be  pure 
mineral  in  character,  and  in  view  of  what  is  said  above,  it  is 
obvious  that  a  heavy  bodied  oil  will  be  needed  for  the  thrust 
blocks,  as  light  bodied  pure  mineral  oils  would  cause  the  thrust 
bearings  to  run  hot. 

Another  condition  in  connection  with  marine  turbines  that 
calls  for  more  viscous  oil  than  similar  size  land  turbines  is  the 
vibration,  which  is  set  up  partly  by  the  turbines  themselves  and 
partly  by  the  reaction  of  the  water  on  the  propellers.  Heavier 
vibration  calls  for  better  cushioning  in  the  bearings,  and  this  can 
only  be  given  by  employing  a  more  viscous  oil. 

Thrust  bearings  of  the  ordinary  type  carry  a  maximum  bearing 
pressure  of  15  Ib.  to  20  Ib.  per  square  inch  in  the  case  of  land 
turbines,  and  30  Ib.  to  50  Ib.  in  the  case  of  marine  turbines. 

Attempts  have  been  made  to  introduce  actual  forced  lubrica- 
tion conditions  in  the  thrust  bearings,  by  making  the  oil  pass 
through  the  hollow  shaft  and  thence  forcing  it  out  between  the 
revolving  thrust  rings  and  'the  stationary  thrust  block.  Such  a 
system  has  been  designed  by  Ferranti,  and  is  said  to  have  given 
excellent  results,  making  it  possible  to  carry  great  pressures 
without  any  fear  of  the  bearing  seizing. 

An  ingenious  method  of  getting  over  the  difficulty  with  the 
thrust  bearing  has  been  designed  by  Franco  Tosi.  He  balances 
the  difference  between  the  propeller  thrust  and  the  steam  thrust 
by  means  of  oil  pressure  exerted  on  the  two  sides  of  a  piston  >vhich 
revolves  with  the  shaft  and  is  fitted  with  a  labyrinth  packing. 
Oil  under  pressure  is  constantly  being  forced  into  the  chambers  on 
both  sides  of  the  piston, and  can  escape  only  between  the  collars 
of  the  thrust  blocks  at  either  side.  If  the  thrust  is  from  right  to 
left,  the  clearances  on  the  left-hand  side  are  diminished,  so  that  it 
is  easier  for  the  oil  to  escape  between  the  right-hand  thrust 


STEAM  TURBINES  209 

collars;  consequently,  the  oil  pressure  becomes  lower  in  the  right- 
hand  chamber  and  the  difference  in  oil  pressure  forces  the  piston 
to  the  right,  or  vice  versa,  thus  automatically  balancing  the  axial 
thrust  and  preventing  metallic  contact  between  the  rings -and 
the  blocks.  At  high  speed  fluid  friction  developed  between  the 
piston  and  its  casing,  etc.  would  be  very  considerable,  but  as 
marine  turbines  are  slow  speed,  this  loss  is  only  small. 

With  Parsons  steam  turbines  the  axial  thrust  on  the  rotor  is 
more  or  less  balanced  by  the  propeller  thrust,  and  the  thrust 
bearing  embodied  in  the  turbine  itself  gives  no  great  difficulty, 
but  with  geared  turbines  with  the  reintroduction  of  a  main  thrust 
block  on  the  propeller  shaft  the  multi-collar  marine  type  of 
thrust  bearing  has  failed  to  give  satisfaction. 

The  even  turning  moment  of  the  turbine  transmitted  through 
the  gearing  never  pulsates  or  fluctuates,  thus  not  giving  the  thrust 
collars  that  relief  which  in  the  case  of  a  steam  engine  in  some  mea- 
sure helps  the  oil  to  creep  in  between  the  rubbing  surfaces. 

For  geared  turbines  the  thrust  problem  has  been  solved  by  the 
Michell  single  collar  thrust  bearing,  described  page  170,  which 
will  carry  a  bearing  pressure  of  400  to  500  Ib.  per  square  inch 
with  the  greatest  of  ease  and  with  a  surface  speed  ranging  from 
60  ft.  to  100  ft.  per  second. 

The  Hon.  Sir  C.  A.  Parsons  has  designed  a  similar  type  of 
bearing,  but  with  centrally  pi  voted  segmental  blocks,  allowing  the 
turbine  shaft  to  revolve  in  either  direction.  The  frictional  losses 
in  these  types  of  bearings  are  considerably  less  than  in  the  ordi- 
nary plain  type  of  thrust  bearing;  the  coefficient  of  friction  may 
be  taken  as  0.002  as  against  0.03  to  0.04  for  ordinary  thrust 
bearings. 

Wear. — As  turbine  bearings  are  virtually  flooded  with  oil, 
it  is  probable  that  the  shaft  never  comes  into  actual  rubbing 
contact  with  the  bearings  except  at  the  moment  of  starting. 
When  the  turbine  is  standing,  the  oil  film  is  pressed  out  and  actual 
contact  between  journal  and  bearing  probably  takes  place,  but 
as  soon  as  the  turbine  starts  running  the  first  few  revolutions 
will  build  up  the  oil  film,  which,  if  the  oil  is  satisfactory,  will 
support  the  shaft;  i.e.,  it  " floats"  on  the  oil  film. 

Turbine  bearings,  speaking  about  the  vast  majority, 
practically  never  wear.  It  sometimes  happens  that  what  may 
appear  to  be  wear  takes  place  for  a  certain  length  of  time,  after 
which  it  ceases;  this  is  in  reailty  due  to  compression  of  the  white 
metal,  which  has  been  rather  soft- 
After  many  years'  working  the  tool  marks  should  still  be 
visible  if  the  turbine  has  had  proper  care  and  attention. 

14 


210  PRACTICE  OF  LUBRICATION 

Temperature  Records. — When  a  turbine  starts  from  cold  the 
oil  will  gradually  rise  in  temperature,  rapidly  at  first,  slowly  later 
on,  and  if  the  conditions  remain  fairly  uniform — uniform  load, 
uniform  temperature  of  cooling  water  and  engine-room — the 
maximum  temperature  will  be  reached  after  a  certain  number  of 
hours,  varying  from  four  hours  in  the  case  of  small  turbines  to 
eight  hours  or  even  longer  in  the  case  of  large  units.  This  final 
temperature  is  not  much  affected  by  changes  in  the  engine-room 
temperature  or  even  by  change  in  load,  but  is,  of  course,  slightly 
higher  with  higher  engine-room  temperature  and  higher  load. 

The  temperature  of  the  cooling  water,  however,  and  the  state 
of  cleanness  of  the  oil  cooler  have  a  marked  influence  on  the  oil 
temperature,  and  naturally  so,  because  it  is  in  the  oil  cooler 
that  the  bulk  of  the  heat  is  removed  from  the  oil,  a  minor  portion 
only  being  radiated  into  the  engine-room  from  the  bearings, 
pedestals,  oil  pipes,  oil  tanks,  etc. 

The  temperature  of  the  oil  in  the  main  return  pipe  ranges  from 
100°F.  to  140°F.,  seldom  below  100°F.  and  not  often  above 
140°F.  But  bearings  have  run  without  trouble  for  long  periods 
at  temperatures  as  high  as  160°F.  However,  it  is  desirable  that 
the  oil  temperature  should  be  about  120°F.  to  130°F. 

In  the  case  of  marine  turbines,  the  oil  temperature  rises  in  the 
Tropics  as  compared  with  conditions  in  temperate  climates; 
due  to  the  higher  temperature  of  the  cooling  water,  being  70°F. 
to  85°F.  as  compared  with  50°F.  to  70°F.  for  temperate  climates. 
The  oil  must  of  necessity  rise  in  temperature  in  order  that  the 
difference  in  temperature  between  itself  and  the  cooling  water 
may  enable  the  water  to  take  away  the  heat  from  the  oil. 

It  would  be  useless  to  quote  actual  temperature  records  from 
turbines  in  operation,  as  they  vary  exceedingly;  for  instance,  in 
some  turbines  the  fall  in  temperature  between  the  return  oil  and 
the  oil  leaving  the  cooler  is  as  low  as  4°F.,  due  to  the  amount  of 
oil  delivered  by  the  oil  pump  to  the  bearings  being  high  per  square 
inch  of  bearing  surface,  and  to  the  bearings  being  water  cooled. 

In  a  good  many  turbines  the  difference  in  temperature  between 
the  outgoing  and  returning  oil  is  from  15°F.  to  20°F.,  and  in 
some  extreme  cases  this  difference  has  been  as  high  as  50°F. 
where  the  bearings  have  not  been  water  cooled  and  the  oil  de- 
livery per  square  inch  of  bearing  surface  has  been  low.  The 
temperature  rise  of  the  oil  going  through  the  worm  wheel  casing 
(the  worm  wheel  shaft  operating  the  oil  pump,  governor,  and 
sometimes  the  circulating  pump  for  the  condensing  plant),  or  the 
thrust  bearing  is  usually  considerably  higher  than  the  tempera- 
ture  rise  of  the  oil  going  through  the  other  bearings. 


STEAM  TURBINES  211 

For  each  particular  turbine  the  temperatures  of  the  oil  and 
water  inlet  and  outlet  to  the  cooler,  and  of  the  oil  inlet  and 
outlet  to  the  various  bearings — or,  as  an  alternative,  the  bear- 
ing temperatures  at  both  ends  of  each  bearing — indicate  whether 
normal  condition  of  lubrication  and  cooling  prevail. 

Thermometer  pockets  filled  with  oil  should  be  fitted  in  the 
positions  mentioned  above.  In  case  of  the  return  oil  tempera- 
tures taken  in  the  bearing  outlets,  care  should  be  taken  that  the 
flow  of  oil  shall  wash  over  the  thermometer  bulb  or  the  pocket. 
Occasionally,  the  thermometers  should  be  compared  with  a 
standard  thermometer,  say  once  a  year.  A  temperature  log 
should  be  kept  in  the  engine-room,  taking  the  temperatures 
every  hour. 

The  turbine  attendants  will' very  soon  get  to  know  by  heart 
the  normal  running  temperatures  at  the  various  points,  and  they 
will  learn  to  interpret  the  correct  causes  of  any  deviations  from 
the  normal  temperatures,  or  at  any  rate  to  look  in  the  right  direc- 
tion for  the  cause  of  irregularities,  indicated  by  abnormal 
temperatures. 

The  Turbine  Glands. — The  most  frequent  cause  of  water 
getting  mixed  with  the  oil  in  circulation  is  leakage  of  steam 
past  the  glands,  the  steam  condensing  on  the  shaft  and  bear- 
ings, gradually  working  its  way  into  the  main  bearings  and 
mixing  with  the  oil.  It  will,  therefore,  be  useful  to  look  for  a 
moment  on  the  various  designs  of  glands. 

There  are  three  types: 

(1)  The  labyrinth  packing  gland. 

(2)  The  carbon  packing  gland. 

(3)  The  water-sealed  gland. 

The  function  of  the  gland  is  either  to  keep  high-pressure  steam 
from  leaking  outward,  or,  in  the  case  of  the  " vacuum  end" 
of  the  turbine,  to  prevent  air  from  being  drawn  in,  which  would 
adversely  affect  the  vacui.  m  produced  by  the  condensing  plant. 

1 .  The  labyrinth  packing  (Fig.  75)  consists  of  a  series  of  rings 
on  the  shaft  which  alternate  with  stationary  rings  in  the  sur- 
rounding casing;  there  is  only  a  very  slight  clearance  between 
the  shaft  and  the  stationary  rings. 

The  steam — in  the  case  of  a  high-pressure  gland — must  pass 
the  rings  in  a  zig-zag  way,  so  that  only  a  slight  amount  of  steam 
escapes  at  the  vent  (1),  which  may  be  connected  with  an  inter- 
mediary stage  of  the  turbine  or  simply  allows  the  steam  to  escape 
into  the  open.  Any  steam  or  water  leaking  outside  the  gland  is 
deflected  by  suitable  throwers  fixed  on  the  shaft  in  order  to 


212 


PRACTICE  OF  LUBRICATION 


prevent  the  water  as  much  as  possible  from  getting  into  the  adja- 
cent bearing. 

In  the  case  of  a  low-pressure  gland,  steam  at  a  reduced  pres- 
sure-either from  an  intermediary  stage  or  high-pressure  steam 
throttled  down  to  the  required  pressure — is  introduced  at  (1) 
and  leaks  inward  into  the  low-pressure  turbine  casing. 


FIG.  75. — Labyrinth  packing. 

The  pressure  should  be  sufficient  to  prevent  air  from  leaking 
in,  that  is  to  say,  sufficient  pressure  should  be  applied  so  that  a 
puff  of  steam  is  just  visible  oozing  out  of  the  gland.  Excessive 
pressure  should  be  avoided,  as  it  means  not  only  waste  of  steam, 
but  also  excessive  condensation  of  steam  on  the  shaft  with  a 
certainty  of  some  of  this  getting  into  the  bearings.  Avoiding 
excessive  condensation  is  particularly  difficult  in  the  case  of  the 
low-pressure  glands  of  exhaust  steam  turbines  with  labyrinth 
packing  glands.  Owing  to  the  variation  in  steam  pressure  it 
becomes  necessary  for  the  attendant  constantly  to  readjust  the 


STEAM  TURBINES 


213 


gland  pressure;  otherwise  either  air  will  occasionally  leak  inward 
or  excessive  leakage  of  steam  will  take  place  outward.  Oc- 
casionally the  glands  are  water  cooled,  as  the  steam  then  con- 
denses on  its  way  through  the  gland  and  consequently  the  thrower 
outside  the  gland  has  to  deal  only  with  water,  which  can  be  much 
more  effectively  thrown  away  from  the  shaft  than  steam. 

2.  The  carbon  packing  (Fig.  76)  consists  of  a  series  of  carbon 
rings,  each  made  up  of  several  sections  and  held  in  their  places 
around  the  shaft  by  means  of  springs.  The  carbon  rings  should 


FIG.  76. — Carbon  packing. 

preferably  not  bear  right  against  the  shaft,  but  on  a  special 
sleeve  fixed  on  the  turbine  rotor  and  slightly  larger  in  bore  than 
the  turbine  shaft,  so  that  should  heavy  wear  take  place  the  shaft 
will  remain  unhurt  and  only  the  sleeve  or  the  packing  itself  will 
get  worn.  No  lubrication  is  needed  of  the  carbon  rings,  but  care 
should  be  taken  that  they  be  a  loose  fit  on  the  cold  shaft,  as 
carbon  contracts  when  heated.  If  grit  and  dirt  get  in,  cutting 
and  wear  may  occur  owing  to  the  absence  of  lubricant,  and 
then  leakage  through  the  packing  will  take  place.  Sometimes 
the  carbon  packing  glands  are  surrounded  with  a  water  jacket, 


214 


PRACTICE  OF  LUBRICATION 


which  causes  a  certain  amount  of  steam  to  condense  in  the  pack- 
ing; this  helps  to  seal  the  gland  and  "lubricate  "  the  carbons.  The 
vent  (1)  serves  the  same  purpose  as  in  Fig.  75. 

3.  The  water-sealed  gland  (see  Fig.  77)  consists  of  a  revolving 
wheel  (1)  formed  with  vanes  on  both  sides  and  acting  like  a 
centrifugal  pump.  The  water  admitted  at  (2)  (or  sometimes  at 
the  circumference  at  (3)  under  a  few  pounds  pressure),  is  thrown 
by  centrifugal  action  to  the  outer  edge  of  (1)  and  thus  establishes 
a  perfect  seal,  it  being  impossible  for  steam  to  escape  round  the 
outer  edge,  the  clearance  being  about  0.01  in.  to  0.02  in.  The 
water  should  be  clean  and  preferably  soft,  as  otherwise  dirt  or 
scale  will  be  deposited  in  the  gland  and  may 
even  get  inside  and  coat  some  of  the  turbine 
blades.  The  water  supply  should  be  kept  as 
1^1  "  low  as  possible  by  regulating  the  quantity 

admitted.  The  second  disc  (4)  revolving  in 
the  groove  (5)  acts  as  another  seal  in  series 
with  (1),  but  the  chief  object  in  fitting  it  is 
to  prevent  water  escaping  from  the  gland  past 
the  groove  (5).  The  water  coming  into  this 
groove  will  be  drained  back  into  the  main 
gland  through  drain  holes  (6)  indicated  at  the 
bottom. 

During  the  time  the  turbine  is  being 
warmed  up  prior  to  starting,  and  where  water- 
sealed  packings  are  employed,  the  vacuum 
cannot  be  created  until  the  turbine  has 
attained  a  certain  speed,  as  the  glands  do 
not  provide  a  perfect  seal  until  the  centri- 
fugal force  is  sufficient  to  prevent  the  air 
from  going  straight  into  the  turbine.  In  case 
°^  mgh-Pressure  water-sealed  glands,  it  is  fre- 
quently desirable  or  necessary  to  watercool 
the  gland  casing,  as  it  otherwise  becomes  so  warm  that  the 
water  evaporates  too  readily  and  gets  into  the  turbine  in  the 
form  of  steam,  and  also,  should  the  water  not  be  very  soft  a 
certain  amount  of  scale  will  be  deposited,  which  is  objection- 
able. It  is  only  at  low  speeds  —  starting  and  stopping  —  that  the 
high-pressure  water-sealed  glands  allow  steam  to  escape,  thus 
making  it  possible  for  condensed  steam  to  enter  the  bearing 
nearest  the  gland  and  mix  with  the  oil  in  circulation. 

GEARED  TURBINES 

The  geared  turbine  of  large  horse  power  has  only  recently  been 
developed,  the  idea  being  to  run  the  turbine  at  high  speed, 


FlGSeaied 


.  STEAM  TURBINES  215 

transmitting  the  power  through  double  helical  gearing  to  a  low 
speed  propeller  shaft — or  generator  shaft — thereby  getting  a  very 
high  overall  efficiency.  The  gears,  when  not  very  accurately 
made,  are  noisy  and  inclined  to  wear,  but  the  latest  developments 
seem  to  be  overcoming  all  obstacles  in  this  direction. 

If  the  gears  are  perfect,  and  as  long  as  they  remain  so,  the  oil 
used  in  the  turbine  can  also  be  used  for  the  gears,  being  con- 
stantly supplied  in  streams  at  the  points  of  contact  between  the 
teeth.  But  if  the  gears  are  inclined  to  be  noisy,  a  heavier  oil 
will  be  preferable  in  order  to  deaden  the  noise.  Such  a  heavy  oil 
will  not  be  satisfactory  in  the  turbine  system,  as  it  will  separate 
only  slowly  from  water  and  dirt  and  cause  high  temperatures 
all  around. 

If  one  oil  system  only  is  used  for  turbine  bearings  and  gearing, 
and  if  the  oil  gets  mixed  with  water — from  the  glands  or  the 
cooler — the  oil  will  suffer  in  the  turbine  system  to  some  extent; 
but  when  this  same  oil,  mixed  with  minute  particles  of  water 
and  dirt,  gets  through  the  gearing  exposed  to  many  times  the 
ordinary  bearing  pressure,  it  is  sure  to  suffer  very  quickly  indeed, 
and  the  result  will  be  wear  of  the  gearing.  For  these  reasons, 
the  author  strongly  recommends  that  the  oiling  system  for  the 
gearing  should  be  made  distinct  and  separate  from  the  oiling 
system  supplying  the  turbine  bearings,  quite  apart  from  the 
question  of  whether  the  same  oil  or  two  different  oils  are  used  in 
the  two  systems.  With  separate  oiling  systems,  the  oil  for  the 
gears  will  remain  dry  and  pure  for  a  much  longer  time,  and  will 
thus  have  a  much  better  chance  of  keeping  the  teeth  of  the  gears 
in  good  condition  and  preventing  wear. 

Treatment  of  the  Oil. — Before  starting  a  new  turbine,  it 
should  be  carefully  cleaned  all  through  the  oil  tanks,  oil  pipes, 
etc.,  in  order  to  remove  as  much  grit  and  dirt,  moulders'  sand, 
rusty  scale,  cotton  waste,  etc.,  as  possible.  Cotton  waste  must 
never  be  used  for  cleaning  purposes,  as  it  leaves  behind  small 
fluffy  pieces,  which  will  tend  to  clog  up  the  oil  pipes  and  particu- 
larly the  fine  clearance  spaces  in  the  oil-worked  governor. 

Mutton  cloths  or  sponges  should  be  used  for  cleaning,  and  it  is 
preferable  to  use  a  cleaning  oil — light  petroleum  distillate  with  a 
higher  flash  point  than  paraffin — rather  than  paraffin,  as  some  of 
the  oil  remains  and  mixes  with  the  lubricating  oil.  Paraffin  will 
commence  to  evaporate  when  the  turbine  starts  running  and 
may  cause  an  explosion.  The  air  should  be  driven  out  of  the 
oil  piping  by  means  of  the  auxiliary  oil  pump,  and  when  the 
pump  is  being  filled  with  oil  it  should  be  put  through  the  sieve 
and  not  direct  into  the  tank,  although  the  latter  may  be  the 
quickest  method. 


210  PRACTICE  OF  LUBRICATION 

After  a  new  turbine  has  been  run  a  month,  during  which  time 
frequent  examinations  of  the  oil  strainer  will  prove  of  interest, 
the  whole  charge  of  oil  should  be  removed,  and  the  oil  tank,  oil 
pipes,  as  well  as  the  bearings,  again  thoroughly  cleaned.  The 
oil  taken  out,  in  which  will  be  found  impurities  of  many  kinds, 
such  as  cotton  waste,  rust,  sand,  dirt,  little  pieces  of  iron,  copper, 
red  lead,  packing  material,  etc.,  should  be  treated  in  a  steam- 
heated  separating  tank,  and  afterward  in  a  good  steam-heated 
filter.  It  can  then,  if  it  was  originally  of  good  quality,  be  used 
as  "make  up"  in  the  circulation  system,  which  in  the  meantime 
has  been  filled  with  a  fresh  charge  of  oil.  This  first  change  of  oil 
may  seem  an  unnecessary  precaution  to  take,  but  it  is  the  author's 
strong  recommendation,  based  on  long  experience,  that  it  should 
always  be  made  and  that  it  pays  in  the  long  run. 

It  is  during  the  early  life  of  a  turbine  that  it  needs  the  greatest 
amount  of  care  and  attention;  later  on  troubles  are  or  ought  to  be 
rare  if  the  oil  is  well  looked  after,  frequently  filtered,  and  the 
strainers  kept  clean.  As  regards  the  inside  of  the  turbine  oil 
chambers,  etc.,  the  surfaces  have  by  some  makers  been  painted; 
this  has  sometimes  been  done  in  order  to  save  the  labor  of 
cleaning  and  scraping  the  surfaces.  In  nine  out  of  ten  cases 
the  paint  itself  has  been  by  no  means  oil  proof,  and  the  result 
has  been  that  the  warm  oil  quickly  dissolved  it,  causing  long 
protracted  troubles  with  the  oil  breaking  down  and  carrying 
sticky  brownish  black  deposits  everywhere  throughout  the  oil 
system.  The  writer  recommends  leaving  the  tanks,  etc.,  un- 
painted,  but  that  the  surfaces  should  be  very  carefully  scraped 
and  cleaned.  Sandblasting  appears  to  be  too  '"searching," 
small  grains  of  sand  being  embedded  in  the  cast-iron  surfaces 
and  involving  a  possibility  of  trouble  later  on.  Steelshot- 
blasting  is  a  very  efficient  method  of  cleaning  the  surface. 

Oil  Filters  and  Settling  Tanks. — When  a  turbine  is  in  normal 
operation  and  has  been  thoroughly  cleaned,  the  amount  of 
impurities  that  gets  mixed  with  the  oil  is  usually  small,  and 
as  far  as  the  oil  circulation  system  itself  is  concerned,  the  only 
precautions  as  regards  filtering  may  be  confined  to  a  good  sieve 
in  the  oil  return  tank,  a  cylindrical  strainer  on  the  pump  suction 
pipe,  or  a  set  of  gauze  strainers.  Ample  capacity  of  the  oil  tanks 
is  always  a  desirable  feature  leading  to  longer  life  of  the  oil 
and  also  giving  the  impurities  and  water  a  chance  to  separate  out. 

A  special  design  of  separating  tanks  was  referred  to  by  Mr. 
A.  H.  Mather  in  a  paper  read  before  the  Institute  of  Marine  Engi- 
neers, October  14th,  1907,  and  under  the  name  of  the  "Two  Tank 
System,"  is  used  in  a  great  many  turbine  ships.  See  ;Fig.  78. 


STEAM  TURBINES 


217 


The  two  tanks  (1)  shown  are  not  intended  to  be  used  concur- 
rently. The  oil  is  allowed  to  rest  in  one  of  the  tanks  for  a  cer- 
tain period,  while  the  oil  circulation  takes  place  through  the 
other.  When  the  oil  has  "rested"  a  sufficient  length  of  time  to 
ensure  complete  separation  from  water  and  other  impurities, 
the  large  drain  cock  (2)  placed  at  the  lowest  part  of  the  tank 
is  opened,  and  the  water,  dirt  and  sludge  are  drained  away  until 
pure  oil  appears.  Means  should  be  provided  to  show  clearly  the 


FIG.  78. — Two  tank  system. 

amount  of  water  in  the  oil,  and  for  this  purpose  a  glass-sided 
box  (3)  is  placed  at  one  end  of  the  tank  in  preference  to  the  ordi- 
nary gauge  glass;  a  strip  of  J^-in.  steel  plate  should  be  placed  at 
the  ends  of  the  box  to  slide  in  a  groove,  the  idea  being  to  prevent 
breakages  of  the  glass,  and  by  lifting  the  steel  sheet  to  enable  one 
to  see  the  amount  of  water  separated  out.  An  air  pipe  (4),  as 
shown  in  the  drawing,  should  be  fitted  to  the  highest  point  of  the 
tank  and  led  to  the  necessary  height.  The  oil  passes  a  filter  (5) 
on  its  way  to  the  oil  pump. 

In  cases  where  a  large  proportion  of  water  finds  its  way  into  the 
oil,  a  heater  might  be  fitted  in  the  return  pipe  to  raise  the  tem- 
perature of  the  oil  to  about  150°F.  This  will  result  in  immediate 


218  PRACTICE  OF  LUBRICATION 

separation  of  all  water  and  foreign  matter  as  soon  as  the  oil  enters 
the  suction  tank,  the  oil  rising  quickly  to  the  top  and  the  sepa- 
rated matter  remaining  at  the  bottom.  To  facilitate  separation, 
the  return  pipe  should  go  almost  to  the  bottom  of  the  tank  and 
deliver  the  oil  in  a  downward  direction.  The  tanks  should  be 
tilted;  the  suction  of  the  pump  should  be  placed  as  high  as  possi- 
ble, the  opening  of  the  pipe  to  be  directed  upward  If  possible. 
The  net  storage  capacity  of  the  tank  is,  of  course,  the  capacity 
above  this  level.  On  leaving  the  tank  the  oil  is  sucked  through 
a  filter  consisting  of  three  or  four  separate  layers  of  gauze  of,  say, 
24  mesh  to  the  inch,  the  uppermost  layer  consisting  of.  two 
sheets  of  gauze  with  a  sheet  of  cheese  cloth  between  them.  The 
bottom  of  the  filter  forms  a  convenient  receptacle  for  any  dirt 
that  may  have  been  carried  as  far  as  this  point,  the  dirt  dropping 
downward  from  the  filter  gauze. 

In  small  and  medium  size  turbine  plants  ashore,  where,  as  a 
rule,  each  turbine  has  its  own  separate  oiling  system,  the  two- 
tank  system  has  only  rarely  been  employed.  The  oil  circulates 
continuously  and  gets  little  rest  when  the  turbine  is  in  operation. 
In  such  plants  it  is  good  practice  to  remove  daily  from  3  to  6  gal- 
lons of  oil  from  each  turbine  unit,  treating  this  oil  in  a  steam- 
heated  separating  tank  and  filter.  The  purified  oil  should  be 
returned  to  the  circulation  system  at  the  same  time  that  a  corre- 
sponding quantity  is  drawn  off  for  treatment.  In  this  way  the 
vitality  of  the  oil  can  be  maintained  at  a  high  standard.  If  the 
oil  tank  capacity  is  small,  it  is  particularly  desirable  to  follow 
this  practice. 

In  large  turbine  power  stations  consisting  of  several  units  it  is 
often  desirable  to  have  a  separate  plant  for  supplying  the  oil  to 
the  various  turbines  and  for  cooling  and  purifying  the  return  oil. 
There  are  several  designs  of  such  plants,  but  common  to  them  all 
is  the  feature  that  a  portion  of  the  oil  is  by-passed  through  a  filter, 
while  the  main  flow  of  oil  is  only  strained  and  cooled,  not  filtered. 
The  oil  coolers,  oil  filters  and  oil  tanks  are  all  made  up  from 
several  identical  units,  so  that  the  necessary  cleaning  and  inspec- 
tion can  be  made  while  the  plant  is  in  operation,  and  without 
disturbing  the  normal  operation  of  the  oil  plant. 

Oil  Consumption. — The  "make  up"  for  lost  oil  due  to  leakage 
and  atomization — there  is  very  little  evaporation — amounts  to 
from  1  pint  to  4  gallons  per  week  per  turbine  unit,  depending 
upon  the  size  and  operating  conditions.  The  average  "make  up" 
for  a  1000-kilowatt  turbine  is  about  1  to  1^2  gallons  per  week. 

Acquired  Impurities. — During  the  passage  of  the  oil  through 
the  entire  circulation  system  it  picks  up  more  or  less  water,  air, 


STEAM  TURBINES  219 

iron  oxides  and  other  impurities,  and  when  passing  through  the 
main  bearings  the  oil  gets  intimately  churned  together  with  these 
foreign  matters;  the  result  is  that,  owing  to  the  high  temperature 
and  the  great  surface  speed  of  the  revolving  shaft,  the  oil 
gradually  breaks  down. 

When  ordinary  oils,  not  specially  manufactured  for  turbine 
use,  are  employed  they  may  not  have  a  life  of  more  than  a  few 
months,  whereas  high  quality  turbine  oil  may  last  under  normal 
conditions  10,000  working  hours  or  more,  and  3,000  working 
hours  under  very  unfavorable  conditions;  also,  the  margin  of 
safety  will  be  considerably  greater  when  using  the  best  possible 
oils.  Whereas  all  oils,  even  the  best,  are  affected  in  time,  un- 
suitable oils  will  sooner  show  the  signs  of  breaking  down,  which 
are  (1)  darkening  in  color;  (2)  increased  specific  gravity;  (3)  in- 
creased viscosity;  (4)  increased  acidity;  and  (5)  the  throwing 
down  of  various  kinds  of  deposits. 

The  first  three  effects  cannot  be  said  to  be  detrimental  except 
that  they  are  the  "  signs  of  warning"  that  the  oil  is  breaking  down. 
As  regards  the  acidity,  the  acid  produced  in  the  oil  is  the  result 
of  oxidation,  and  is  a  petroleum  acid  which  must  not  be  confused 
with  sulphuric  acid,  which  is  sometimes  found  in  mineral  oils 
that  have  been  treated  with  this  acid  during  their  manufacture. 
Petroleum  acids  do  not  attack  the  metals  ordinarily  used  in  the 
construction  of  the  circulation  system,  but  they  do  slowly  dis- 
solve zinc  or  alloys  consisting  largely  of  that  metal.  Increased 
acidity  can  always  be  taken  as  a  guide  to  judge  how  far  the  oil 
has  suffered,  and  when  it  gets  in  the  neighborhood  of  0.3  per 
cent,  in  terms  of  S03,  steps  should  be  taken  to  prevent  this  limit 
being  exceeded,  by  renewing  either  part  of  the  oil,  or  all  of  it,  as 
the  circumstances  may  seem  to  justify.  When  the  acidity  of  an 
oil  is  below  0.03  per  cent,  it  is  generally  considered  by  chemists 
to'  be  "free  from  acid;"  good  turbine  oils  often  contain  less  than 
0,008  per  cent,  of  acidity,  when  new. 

DEPOSITS 

Deposits  may  form  even  where  the  best  oils  are  in  use,  although 
always  in  very  much  smaller  quantities  than  where  unsuitable 
oils  are  employed.  Naturally,  it  is  the  constant  aim  and  en- 
deavor of  the  oil  manufacturer  to  produce  oils  which  possess  as 
great  a  resistance  as  possible  against  the  oxidizing  and  emulsi- 
fying effect  of  the  impurities,  etc. 

The  principal  causes  of  deposit,  apart  from  the  quality  of  the 
oil,  are:  (1)  water;  (2)  solid  impurities;  (3)  air;  (4)  electric  action; 
(5)  adding  new  oil. 


220  PRACTICE  OF  LUBRICATION 

1.  Water. — Water  has  an  emulsifying  effect  on  the  oil,  par- 
ticularly if  it  contains  impurities,  whether  in  solution  or  suspen- 
sion. Where  considerable  quantities  of  water  leak  into  the 
system  and  emulsification  takes  place,  the  oil  becomes  yellow  or 
brownish  yellow  in  color,  and  if  a  sample  is  taken  out  and  heated 
it  will  separate  into  clean  oil  at  the  top,  more  or  less  milky  water 
at  the  bottom,  and  a  spongy  sludge  separating  the  oil  and  water. 
If  the  oil  and  the  water  are  removed,  the  spongy  emulsion,  which 
varies  in  color  from  gray  to  brown,  will  be  found  to  contain 
from  15  per  cent,  to  35  per  cent,  of  oil  and  to  consist  of  numerous 
exceedingly  thin  films  of  oxidized  matter  surrounding  small 
drops  of  water;  in  fact,  the  sludge  when  freed  from  oil  consists  of 
about  99  per  cent,  water  by  weight,  and  1  per  cent,  of  exceedingly 
thin  films.  On  analysis  these  films  have  been  found  to  be  com- 
posed of  a  chemical  combination  of  petroleum  acids  produced  by 
decomposition  of  the  oil,  and  rust  (iron  oxides)  which  is  found 
throughout  the  system. 

The  nature  of  the  sludge  in  the  oil  produced  by  the  water  is 
most  objectionable,  as  it  tends  to  clog  the  oil  strainers,  oil  inlets 
to  the  bearings,  and  oil  inlet  to  the  governor.  Furthermore,  the 
oil  pressure  may  be  reduced,  due  to  the  oil  pump  not  delivering 
the  requisite  quantity  of  oil  because  of  the  partial  choking  of  the 
pump  strainers.  The  chief  source  of  water  getting  into  the  oil 
is  usually  the  gland  packings;  water  may  also  leak  into  the  oil  in 
the  oil  cooler  or  in  the  bearings  (when  water  cooled).  On  sea- 
going ships  a  leakage  of  cooling  water  into  the  oil  can  be  detected 
at  once  by  taste,  the  cooling  water  being  salt.  If  one  could 
always  be  sure  of  the  steam  passing  the  glands  producing  an 
absolute  soft  water  of  condensation  free  from  boiler  salts,  it 
would  be  an  easy  matter  by  analysis  to  determine  whether  the 
water  leaking  into  the  oil  was  from  the  glands  or  from  the-cooler, 
or  partly  from  one,  partly  from  the  other  source.  But  when 
the  boilers  prime,  such  analysis  becomes  almost  useless,  for 
obvious  reasons.  Determining  the  degree  of  hardness  of.  the 
water  drawn  away  from  the  oil  in  the  system  is  quite  misleading, 
as  the  acidity  of  the  water — washed  out  of  the  oil — upsets  the 
titration  test.  Evaporating  the  water  to  dryness  and  ignoring 
the  percentage  of  metallic  salts — iron,  copper,  etc. — which  the 
water  has  dissolved  from  the  oil  pipes,  and  comparing  the  grains 
of  salts  remaining  with  the  results  when  evaporating  a  similar 
volume  of  cooling  water,  is  about  the  only  reasonably  accurate 
chemical  method  of  forming  an  idea  as  to  where  the  leakage  occurs. 

Mechanically,  it  is  often  possible,  sometimes  even  quite  easy  to 
locate  the  leakage. 


STEAM  TURBINES  221 

Where  leakage  of  water  into  the  oil  system  cannot  very  well  be 
avoided,  a  " water  leg"  consisting  of  at  least  4  feet  of  vertical 
pipe — 2^  inches  to  4  inches  in  diameter — fitted  to  the  bottom  of 
one  of  the  oil  tanks  may  do  great  service,  as  it  will  catch  the  fine 
drops  or  particles  of  water  circulating  with  the  oil,  and  once  a 
particle  is  caught  in  the  "leg"  it  cannot  again  rise  and  mix  with 
the  oil;  it  goes  to  the  bottom  of  the  leg,  which  should  be  drained 
twice  every  24  hours.  Strict  instructions  should  be  given  that 
the  drain  cocks  in  the  oil  tank  or  tanks  should  be  opened  twice 
every  24  hours,  and  every  time  the  turbine  is  about  to  start  up 
after  a  rest;  the  drains  should  be  kept  open  until  clean  oil  appears. 

Turbine  oils  are  affected  by  water  if  it  contains  boiler  salts  in 
solution,  more  than  by  clean  water,  and  certain  boiler  compounds 
have  a  strong  emulsifying  effect,  but  the  greatest  effect  seems  to 
be  produced  by  iron  salts  in  solution.  The  water  cannot  help 
dissolving  some  of  the  iron  during  its  rapid  flow  through  the  oil 
pipes,  hence  the  desirability  of  using  copper  oil  pipes  in  preference 
to  iron  pipes;  copper  is  little  attacked  by  water,  and  a  copper 
solution  ha.s  only  a  slight  emulsifying  effect  on  the  oil  as  compared 
with  the  effect'  of  an  iron  solution. 

2.  Solid  Impurities.  —  The   disintegrating   effect   on   the  oil 
caused  by  finely  suspended  solid  impurities,  such  as  fine  rust, 
moulders'  sand,  etc.,  is  very  marked.     The  oil  darkens  consider- 
ably in   color,  the  acidity  increases  rapidly;  the  oil  assumes 
a  " burnt"   odor,   a  slimy  dark  colored  deposit  develops  and 
lodges,  particularly  in  the  oil  cooler.     If,  furthermore,  there  is  a 
leakage,  however  slight,  of  water  into  the  oil  system,  the  oil 
may  get  badly  emulsified,  much  more  than  would  be  the  case 
with  water  alone,  as  the  oil  is  in  a  weakened  condition  due  to  the 
oxidizing  effect  of  the  solid  impurities.     This  will  explain  why, 
when  a  new  turbine  is  being  started  up  for  the  first  time,  emulsi- 
fication  of  the  oil  may  occur  even  if  the  oil  is  of  good  quality. 

Where  the  inside  of  the  oil  tank  is  painted,  emulsification  and 
breakdown  of  the  oil  usually  occurs,  as  there  exist  hardly  any 
paints  that  are  "oil-proof"  under  the  exacting  conditions  pre- 
vailing in  turbine  practice.  The  advisability  of  changing  the 
initial  charge  of  oil  will,  in  view  of  what  is  said  above,  now  be 
fully  understood,  the  effect  being  that  the  entire  system  gets 
thoroughly  cleaned,  and  that  the  fresh  charge  of  oil  will  have 
very  much  better  conditions  to  work  under. 

3.  Air.     The  circulating  oil  always  contains  more  or  less  air, 
and   when  the   temperature  is  above  normal,   say  more  than 
140°F.,  this  air  has  a  tendency  to  oxidize  the  oil,  a  tendency  that 
increases  rapidly  with  increasing  temperatures.     This  effect  will 


222  PRACTICE  OF  LUBRICATION 

be  better  realized  when  considering  that,  the  oil  film  in  the  bear- 
ings is  very  thin  and  that  the  air  is  present  in  exceedingly  fine 
bubbles,  which  are  intimately  mixed  with  the  oil.  The  result  is 
that  the  oil  darkens  in  color,  increases  in  acidity,  and  in  extreme 
cases  a  black,  carbonaceous  deposit  develops,  which  is  exceed- 
ingly dangerous,  as  it  may  choke  the  oil  inlets  to  the  bearings 
and  cause  sluggish  working  of  the  governor  gear,  or  may  even 
cause  it  to  stick,  putting  the  governor  out  of  action. 

Another  effect  of  air  in  the  oil  shows  itself  only  when  an  abnor- 
mal amount  is  present;  the  effect  is  known  as  " fuming."  Fumes 
issue  from  the  main  bearings  and  oil  tank,  notwithstanding  that 
the  bearing  temperatures  are  quite  normal;  the  fumes  may  be 
drawn  into  the  generator  windings  and  cause  disastrous  results. 
The  cause  of  the  " fumes"  is  that  the  fine  air  bubbles,  with  which 
the  oil  is  heavily  charged,  burst  in  the  bearing  cavities  and  in 
the  oil  tank,  producing  a  very  fine  spray  of  oil  that  oozes  out  in 
the  form  of  a  mist — the  oil  "fumes."  The  oil  will  be  found 
creeping  all  over  the  outside  of  the  bearings  and  turbine  bed- 
plate, forming  a  very  thin  film,  and  the  loss  of  oil  may  be  quite 
considerable,  several  gallons  per  24  hours.  The*  remedy  is  to 
prevent,  as  far  as  possible,  the  oil  from  getting  churned  together 
with  the  air.  Perhaps  the  churning  takes  place  between  oil 
throwers  and  baffle  plates  inside  the  bearings,  or  the  oil  gets 
violently  disturbed  in  the  sight-feed  arrangements  in  the  return 
pipes,  or  where  the  return  branch  pipes  join  the  main  return 
pipe,  etc.  If  the  spray  is  formed  inside  the  bearings  these  should 
be  ventilated,  a  large  pipe  connection  being  taken  from  the  air 
space  in  the  bearing  cavities  to  the  oil  return  tank.  The  "  fumes  " 
will  then  go  through  these  pipes  instead  of  oozing  out'  of  the 
bearing  ends;  sometimes  enlarging  the  oil  return  pipes  will  over- 
come the  trouble.  The  main  return  oil  tank  should  always  have 
a  vent  pipe,  at  least  1  inch  in  diameter,  to  prevent  accumulation 
of  oil  "fumes"  in  this  tank  and  in  the  return  oil  pipes.  Frothing 
may  also  occur  temporarily  when  a  considerable  percentage  of  the 
oil  in  circulation  is  renewed  at  one  time,  say,  50  per  cent.  New 
oil  should  always  be  added  in  small  quantities  at  a  time. 

4.  Electric  Action. — If  in  the  case  of  the  electric  generator 
there  is  a  slight  leakage  of  electric  current  from  the  generator 
(direct-current  generator)  or  if  the  magnetic  field  is  out  of  balance 
(alternating-current  generator),  and  produces  induced  currents 
in  the  turbine  shaft,  the  result  is  that  an  electric  current  passes 
through  the  shaft  down  through  one  of  the  main  bearings, 
through  the  bed-plate  and  up  through  another  main  bearing 
back  into  the  shaft.  The  effect  on  the  oil  is  that  it  quickly 


STEAM  TURBINES  223 

darkens  in  color,  increases  in  acidity,  and  throws  down  a  deposit 
which  coats  all  parts  of  the  turbine  with  which  it  comes  in  con- 
tact, lodging  particularly  in  the  oil  cooler.  The  deposit  is  of  a 
fairly  hard,  brittle  nature,  and  of  dark  chocolate  color;  it  is 
exceedingly  difficult  to  remove,  and  therefore  very  objectionable. 
The  remedy  is  completely  to  insulate  electrically  one  of  the  main 
bearings  from  the  turbine  bed-plate,  including  the  connections 
between  the  oil  pipes  and  that  particular  bearing.  This  insula- 
tion will  prevent  the  formation  of  an  electrical  current,  and  con- 
sequently the  formation  of  deposits  will  cease. 

On  rare  occasions  local  galvanic  currents  may  cause  corrosion 
of  the  oil  tubes  in  the  oil  cooler,  or  of  the  turbine  shaft  and  bear- 
ings, and  even  in  the  governor,  causing  the  oil-operated  piston  to 
stick,  or  may  eat  away  the  sharp  edges  of  the  pilot  valve. 

5.  Adding  New  Oil. — Where  practically  no  water  enters  the 
circulation  system  and  where  practically  no  waste  or  leakage  of 
oil  occurs,  so  that  the  amount  of  new  oil  added  to  the  system  per 
week  is  only  very  small,  the  oil  in  time  becomes  very  dark  in 
color,  and  the  acidity  increases  considerably.  In  such  cases  it 
has  been  found  that  when  new  oil  is  added  a  dark  deposit  is 
thrown  down  throughout  the  system,  owing  to  the  action  of  the 
old  oil  on  the  new,  and  this  is  particularly  the  case  with  heavy 
viscosity  oils  rather  than  with  light  oils. 

Speaking  generally,  deposits  are  always  inclined  to  accumulate 
in  the  most  dangerous  places,  such  as  the  oil  pipes  leading  from 
the  majn  oil  pipe  into  the  main  bearings.  A  partial  choking  of 
the  oil  inlet  would  reduce  the  oil  feed,  the  bearing  would  heat  up 
quickly,  and  if  not  observed  in  time  the  bearing  surfaces  would 
with  all  certainty  be  destroyed,  which  might  have  very  serious 
consequences,  owing  to  the  Tiigh  speed  at  which  all  turbines 
operate,  and  particularly  so  on  account  of  the  time  it  takes — half 
an  hour  or  more — for  the  turbine  to  come  to  rest  from  full  speed. 
If  deposits  get  into  the  oil  pipe  feeding  the  governor  gear,  the 
governor  may  fail  to  act,  and  consequently  the  turbine  would 
either  gradually  slow  down  or  increase  in  speed  much  above  the 
normal  speed.  The  parts  inside  the  governor  gear  in  contact 
with  the  oil  are  very  sensitive — with  small  clearances — and  the 
oil  must  be  absolutely  clean  and  good  in  order  to  make  the 
parts  work  smoothly. 

TYPICAL  EXAMPLES  OF  TURBINE  TROUBLES 

Example  No.  I.—IQOQ-K.W.  Turbine,  3000  R.P.M. 

Temperature  of  oil  leaving  bearings 120°F. 

Temperature  of  oil  leaving  cooler 110°F. 

Quantity  of  oil  in  circulation 60  gallons, 


224  PRACTICE  OF  LUBRICATION 

The  oil  cooler  contained  100  copper  pipes  21  mm.  diameter  and 
1  meter  long,  the  oil  being  sucked  from  the  cooler,  with  the  result 
that  a  slight  amount  of  water  was  always  leaking  into  the  oil  in 
the  cooler  owing  to  the  thin  copper  tubes  not  keeping  quite 
watertight  in  the  endplates.  The  cooling  water  was  taken  from 
a  brook;  it  was  practically  soft  water  and  for  several  years  no 
trouble  had  been  experienced.  The  oil  in  use  was  similar  to 
Circulation  Oil  No.  1  (page  236)  and  gave  complete  satisfaction. 
Suddenly  trouble  commenced.  An  emulsified  sludge  was  formed 
throughout  the  oil  system  and  the  bearing  temperatures  increased. 
It  was  found  necessary  to  change  the  oil  every  three  or  four  weeks, 
whereas  previously  the  oil  (without  any  daily  treatment)  was 
renewed  only  every  six  months. 

A  thorough  examination  revealed  the  fact  that  the  oil  cooler 
was  leaking  and  furthermore  that  the  water  supply  had  been 
changed.  The  water  instead  of  being  taken  from  the  brook  was 
taken  from  the  coal  washing  plant,  after  indifferent  filtration;  it 
contained  coal  dust  and  was  exceptionally  hard.  An  emulsifi- 
cation  test  with  fresh  oil,  using  this  water,  showed  unsatisfactory 
separation  and  explained  the  cause  of  the  trouble. 

As  a  result  of  the  higher  bearing  temperatures  which  had 
prevailed  for  several  months  a  large  amount  of  sludge  had  settled 
in  the  oil  cooler  and  gradually  baked  into  a  fairly  hard  deposit 
which  almost  choked  the  cooler. 

Example  No.  2.— 3000-#.  W.  Turbo-generator. 

Oil  temperature  of  bearings 120-130°F. 

Quantity  of  oil  in  circulation 120  gallons. 

Rate  of  circulation Exceptionally  rapid. 

A  certain  amount  of  sludge  was  continuously  developed  in  the 
oil  system  and  settled  at  the  bottom  of  the  turbine  bed  chamber. 
Two  samples  were  drawn  at  an  interval  of  seven  weeks  and  were 
analyzed  as  follows : 


|  Sample  No.  1, 
per  cent. 

Sample  No.  2, 
per  cent. 

Oil     . 

•12 

17 

Water 

22 

36 

Sludge  

66 

47 

Sludge. 
Water  ';  

45  1 

43  0 

Oil  

34  2 

34  2 

Volatile  matter  insoluble  in  petroleum  spirit. 
Ash  (containing  oxides  of  iron,  silica  and  lead). 
Petroleum  acids  . 

.      18.5 
.        2.2 
1  389  as 

20.0 
2.8 
1    'iQS    as 

Oil. 
Acidity 

S03 
0  154 

SO3 
0  21  R 

Color,  Lovibond  VA!'  cell.  . 

125 

179 

STEAM  TURBINES  225 

It  will  be  seen  that  the  color  of  the  oil,  which  when  the  oil 
is  new  is  about  35  has  darkened  considerably,  also  that  the  acidity 
of  the  oil  and  sludge  has  increased  between  the  dates  of  taking 
the  two  samples.  The  cause  of  the  deposit  is  emulsification 
and  oxidation  of  the  oil,  brought  about  by  the  rapid  circulation 
(aeration  of  the  oil),  and  also  the  very  small  volume  of  oil  in 
circulation.  Only  a  small  amount  of  water  was  leaking  into 
the  system,  but  owing  to  the  very  rapid  circulation  of  the  oil  the 
water  was  never  given  a  chance  to  separate  out. 

Example  No.  3. — Four  large  turbines  were  using  an  exceptionally 
heavy  turbine  oil  similar  to  Circulation  Oil  No.  3.  The  bearing 
temperatures  were  high,  from  150-165°F.  and  the  oil  coolers 
were  constantly  filling  up  with  a  thick  sludge.  An  investiga- 
tion proved  that  the  boilers  were  priming.  The  boiler  salts 
carried  over  with  the  steam  found  their  way  through  the  turbine 
glands  into  the  bearings,  contaminating  the  oil  and  causing  the 
sludge.  Owing  to  the  fact  that  the  oil  was  far  too  viscous  for 
the  conditions  the  accumulative  effect  of  the  water  charged  with 
boiler  salts  was  very  troublesome. 

A  change  in  grade  of  oil  to  a  light  viscosity  oil  similar  to 
Circulation  Oil  No.  1  was  made  with  the  result  that  the  bearing 
temperatures  were  reduced  to  120-130°F.  and  at  the  same  time 
an  efficient  system  of  daily  treatment  of  the  oil  in  the  turbine 
was  instituted.  It  was  then  found  that  very  little  sludge  formed 
in  the  system  and  the  little  which  did  form  was  largely  removed 
from  the  oil  by  the  process  of  daily  treatment. 

Example  No.  4. — That  an  admixture  of  fixed  oil,  whether 
vegetable  or  animal,  quickly  causes  trouble  when  water  is  present 
is  obvious,  and  usually  very  soon  detected.  The  following  ex- 
ample is  of  interest  in  this  connection. 

A  new  grade  of  turbine  oil  was  tried  on  board  a  large  turbine 
steamer,  the  entire  system  being  cleaned  out  and  filled  with  the 
new  oil.  On  the  first  trip  of  the  boat  the  oil  got  badly  emulsified 
and  the  Chief  Engineer,  complaining  bitterly,  insisted  upon  re- 
verting to  the  old  oil.  Careful  examination  proved,  however, 
that  there  was  a  small  percentage  of  saponifiable  matter  present 
in  the  turbine  system  and  in  the  turbine  oil  supply  tanks  on 
board  the  boat;  and  strangely  enough  the  percentage  of  saponifi- 
able matter,  althouuh  very  small,  was  greater  in  the  oil  circulating 
in  the  turbine  than  in  the  oil  in  the  supply  tanks.  It  was  evident 
that  some  compounded  marine  engine  oil  had  been  "  accidentally  " 
added  to  the  system  and  evidently  a  slightly  greater  proportion 
had  been  added  into  the  turbine  system  than  into  the  supply 
tanks. 

15 


226  PRACTICE  OF  LUBRICATION 

In  connection  with  marine  steam  turbines  great  care  must 
be  exercised  to  prevent  contamination  with  marine  engine  oils, 
which  are  always  compounded  with  vegetable  or  animal  oils. 
This  point  must  be  paiticularly  watched  in  case  of  large  warships 
where  oil  is  pumped  on  board  through  a  flexible  hose;  a  separate 
line  must  be  used  for  turbine  oil. 

Example  No.  5. — In  a  large  turbine  shortly  after  erection 
the  bearing  temperatures  commenced  to  rise  and  a  tenacious 
emulsified  sludge  developed  throughout  the  system.  It  was 
found  that  the  water  softening  plant  for  treating  the  boiler  water 
had  not  been  properly  looked  after,  excess  soda  getting  into  the 
boilers.  Priming  of  the  boilers  carried  soda  into  the  turbine, 
and  through  the  glands  it  finally  reached  the  oiling  system.  The 
turbine  bed  chamber  was  painted  with  " oil-proof"  paint,  but 
the  soda  very  soon  dissolved  or  destroyed  it  and  mixing  with  the 
water  brought  about  the  emulsification. 

Example  No.  6.—- 3,000-K.TF .  Turbine.  An  oil  similar  to  Circu- 
lation Oil  No.  1  and  of  good  quality  was  in  use.  Oil  tempera- 
tures were  normal,  being  approximately  120°F.  The  quantity 
of  oil  in  circulation  was  60  gallons;  the  oil  was  drawn  through 
the  cooler  by  the  oil  pump,  so  that  the  oil  was  always  under 
suction.  Very  little  water  leaked  into  the  oil  system,  being 
approximately  one  pint  per  24  hours;  the  oil  gave  excellent 
results  and  was  renewed  only  once  a  year.  A  thin  deposit 
developed  in  the  oil  cooler  having  the  following  composition : 

Oil  with  a  trace  of  moisture 46.  4  per  cent. 

Volatile  matter  insoluble  in  petroleum  spirit .  48 . 9  per  cent. 

Fixed  carbon  and  oxides  of  silica 0.1  per  cent. 

Iron  oxides 2.2  per  cent. 

Copper  oxides 2.0  per  cent. 

Balance  undetermined , ,  .  0.4  per  cent. 

A  sample  of  the  water  leaking  into  the  oil  system  was  analyzed 
and  found  to  be  very  hard,  similar  to  the  cooling  water.  Ob- 
viously what  had  happened  was  that  the  cooling  water  had  con- 
stantly leaked  into  the  oil  system;  owing  to  the  small  volume  of 
oil  in  rapid  circulation  considerable  aeration  took  place  and  the 
combined  effect  of  the  air  and  water  was  to  produce  slowly  the 
deposit  which  was  found  in  the  oil  cooler. 

This  and  Example  No.  1  point  to  the  desirability  of  always 
having  the  oil  under  a  pressure  in  the  oil  cooler  higher  than  the 
pressure  of  the  cooling  water. 

Example  No.  7. — A  1,500-K.W.  turbine  had  for  several  years 
been  using  an  oil  similar  to  Circulation  Oil  No.  1  with  every 
satisfaction. 


STEAM  TURBINES 


227 


Quantity  of  oil  in  circulation 80  gallons. 

Bearing  temperatures Quite  normal. 

Suddenly  the  bearing  temperature  rose  within  one  week  from 
about  110°F.  to  140°F.  On  examination  it  was  found  that  a 
thick  deposit  had  developed  and  nearly  choked  the  oil  coolers. 
The  deposit  on  analysis  gave  the  following  composition  :- 

Oil  and  water 42 . 8  per  cent. 

Volatile  matter  insoluble  in  petroleum  spirit .  .  17.8  per  cent. 

Fixed  carbon  and  oxides  of  silica 1.6  per  cent. 

Oxides  of  iron 36 . 4  per  cent. 

Balance    undetermined,     containing    copper 

oxides,  etc 1.4  per  cent. 

Analysis  of  the  oil  showed  that  it  was  in  very  good  condition, 
the  percentage  of  petroleum  acids  being  only  0.05  per  cent.  It 
was  somewhat  dark  in  color  and  heavier  in  viscosity  than  the 
fresh  oil,  but  nothing  to  be  alarmed  about. 

On  the  oil  pipes  being  taken  apart  it  was  found  that  during 
five  years'  operation  the  pipes  had  rusted  on  the  inside,  and  a 
portion  of  the  rust  had  been  either  absorbed  by  the  water  cir- 
culating with  the  oil  or  circulated  in  the  form  of  a  fine  powder. 

As  mentioned  elsewhere  finely  divided  iron  and  iron  salts  have 
a  very  powerful  effect  on  turbine  oils.  This  explains  the  forma- 
tion of  the  sludge  which  almost  put  the  oil  coolers  out  of  action 
and  brought  about  the  high  bearing  temperatures. 

Example  No.  8. — 1700-K.W.  TURBOGENERATOR,  3000  R.F.M. 

Quantity  of  oil  in  circulation 60  gallons. 

Temperature  of  oil  leaving  bearings Approximately  150°F. 

Temperature  of  oil  leaving  cooler 140°F. 

Great  trouble  was  experienced  in  this  turbine  with  oxidation. 
A  black  brittle  deposit  developed  throughout  the  system,  set- 
tling particularly  in  the  oil  cooler  and  in  the  oil  inlets  to  the  bear- 
ings, also  in  the  governor  gear,  preventing  the  governor  from 
functioning  properly. 


Unused 


Used 


Oil. 

Specific  gravity 

Open  flash  point    \  Unaltered. 

Fire  point 

Saybort  viscosity  at  104°F 

Color 

Petroleum  acids  as  SOS 

Deposit. 

Volatile  matter  insoluble  in  petroleum  spirit..  . 
Ash,  chiefly  iron  oxides 


135" 

40 

0.006% 


153" 
400 
0.08% 

95.2% 
4.8% 


228  PRACTICE  OF  LUBRICATION 

The  analysis  given  in  the  proceeding  table  compares  the  unused 
oil  and  the  oil  after  four  months  use: 

It  is  obvious  that  the  temperature  of  the  oil  in  circulation 
was  too  high  and  the  amount  of  oil  in  circulation  too  small, 
with  the  result  that  the  oil  was  quickly  oxidized. 

Example  No.  9. — -A  large  turbine  suddenly  developed  high 
bearing  temperatures,  and  an  investigation  proved  that  the  verti- 
cal oil  cooler  had  become  air  locked,  the  upper  part  of  the  oil 
cooler  thus  being  put  out  of  action.  The  obvious  remedy  was  to 
fit  an  air  vent  pipe,  leading  the  air  from  the  uppermost  part  of 
the  oil  cooler  up  to  the  main  oil  return  tank. 

Example  No.  10. — A  1000-K.W.  steam  turbine  immediately 
after  erection  was  greatly  troubled  with  oil  vapors  oozing  out 
of  the  turbine  bedplate  (used  as  the  oil  reservoir),  which  meant 
not  only  a  large  waste  of  oil  but  also  a  considerable  danger  to 
the  generator. 

An  investigation  proved  that  the  oil  return  pipes  from  the 
bearings,  instead  of  sloping  gradually  into  the  bedplate,  were 
vertical;  the  return  oil  falling  into  the  reservoir  caused  the  oil 
to  splash  about  and  form  a  great  deal  of  oil  spray.  The  return 
oil  pipes  were  then  altered  and  the  trouble  ceased. 

Example  No.  11. — A  1500-K.W.  steam  turbine  was  greatly 
troubled  with  oil  vapors  which  evidently  emanated  from  the 
main  bearings,  and  the  presence  of  oil  in  the  generator  was  clearly 
visible.  Everything  possible  had  been  tried  to  stop  the  vapors 
emanating  from  the  bearings,  when  on  an  investigation  by  an  oil 
expert  it  was  found  that  the  return  oil  tank  had  no  vent  pipe, 
and  that  the  fine  oil  spray  developed  in  the  bearings  could  not 
pass  back  into  the  oil  tank,  but  simply  filled  up  the  oil  return 
pipes  and  then  had  to  find  its  way  out  through  the  bearing 
ends.  The  obvious  remedy  was  applied  and  the  trouble  thus 
overcome. 

Example  No.  12.— A  1500-K.W.  Howden  turbine,  3,000  R.P.M. 
was  using  an  oil  similar  to  Circulation  Oil  No.  2  and  of  good 
quality.  Difficulties  were  experienced  with  the  oil  "'creeping" 
along  the  turbine  shaft  and  getting  into  the  generator. 

An  investigation  proved  that  the  oil  was  unnecessarily  viscous 
for  the  conditions  and  an  oil  similar  to  Circulation  Oil  No.  1  was 
installed  to  see  whether  the  change  in  oil  would  make  any  differ- 
ence. Curiously  enough  the  "creeping"  of  the  oil  entirely  dis- 
appeared without  the  Engineer  being  able  to  offer  any  definite 
explanation  as  to  the  reason  why  it  ceased.  At  the  same  time  a 
remarkable  difference  in  the  bearing  temperatures  took  place  as 
shown  in  the  following  table : 


STEAM  TURBINES 


229 


Old  oil, 


New   oil, 


No.  1  bearing       

130 

116 

No  2  bearing 

124 

110 

No.  3  bearing  

122 

108 

No.  4  bearin01 

123 

108 

No.  5  bearing  

134 

122 

No.  6  bearing     

116 

106 

Temp  of  inlet  oil 

110 

98 

Temp,  of  outlet  oil  

130 

114 

Temp  inlet  cooling  water 

48 

48 

Temp,  outlet  cooling  water  
Temp,  engine  room     ... 

78 
80 

68 
79 

The  above  figures  show  clearly  the  lower  bearing  tempera- 
tures obtained  by  using  the  low  viscosity  oil,  notwithstanding 
that  the  supply  of  town  water  through  the  oil  cooler  was  greatly 
decreased  when  the  new  oil  had  been  installed;  as  town  water  had 
to  be  paid  for  the  change  in  oil  brought  about  quite  a  considerable 
saving  in  the  water  bill. 

Note:  Where  oxidation  takes  place  due  to  oil  temperatures 
being  too  high,  a  change  to  lighter  viscosity  oil  has  often  reduced 
temperatures  and  stopped  the  oxidation. 

Example  No.  13.— 350-K.W.  Mixed  Pressure  Turbine,  3,000  It. P.M. 

Temperature  of  oil  leaving  bearings 120°F. 

Temperature  of  oil  leaving  cooler. 105°F. 

Quantity  of  oil  in  circulation 60  gallons. 

Oil  consumption 1  gallon  per  week 

added  to  the  system. 

The  turbine  was  in  operation  day  and  night  continuously  until 
it  had  to  be  stopped  owing  to  the  armature  of  the  generator 
breaking  down.  Before  the  turbine  was  stopped  the  oil  tem- 
peratures had  for  several  weeks  been  gradually  creeping  up,  for 
some  unknown  reason.  When  the  turbine  was  opened  up  for 
inspection  the  flexible  coupling  between  the  turbine  and  the  gen- 
erator was  found  to  be  absolutely  solid  with  a  black  brittle  car- 
bonaceous deposit,  which  was  also  found  throughout  the  entire 
oil  system. 

Strangely  enough  there  was  no  perceptible  wear  of  any  of  the 
bearings ;  the  surfaces  of  the  brasses  were  black  and  dull,  covered 
with  a  very  slight  deposit.  The  oil  from  the  turbine  had  a 
charred  odor  and  a  dark  brown  bloom,  whereas  the  bloom  of  the 
fresh  oiKwas  .green.  It  was  apparent  that  a  radical  change  had 
taken  place  in  the  oil.  The  deposit  consisted  of: 


230  PRACTICE  OF  LUBRICATION 

Per  cent. 

Oil  and  volatile  matter  insoluble  in  petroleum  spirit,  with  a 

slight  percentage  of  water 77 . 4 

Fixed  carbon 2.4 

Iron  oxides 10 . 5 

Copper  oxides 8.4 

Undetermined,  containing  carbonate  of  magnesia ,  traces  of 

lead,  etc 1.3 

The  total  amount  of  the  deposit  was  about  25  Ib.  and  a  large 
portion  of  this  had  undoubtedly  been  in  constant  circulation  with 
the  oil  in  the  form  of  very  fine  powder  which  settled  when  the 
turbine  was  stopped.  Owing  to  a  fault  in  the  rotor  and  armature, 
stray  currents  had  passed  down  through  the  bearings,  oil  pipes, 
oil  cooler,  etc.,  and  had  caused  the  oil  to  break  down,  developing 
the  deposit. 

The  remedy,  apart  from  putting  the  rotor  in  order,  was  to  en- 
tirely insulate  the  end  bearing  of  the  turbine  from  the  bed  plate. 
This  practice  is  now  followed  by  a  good  many  turbine  builders 

Example  No.  14. — A  1000-K.  W.  exhaust  steam  turbo-generator 
had  an  electric  breakdown  similar  to  the  turbine  mentioned  in 
Example  No.  13.  The  oil  used  underwent  a  remarkable  change 
in  the  course  of  one  week,  becoming  changed  in  color  from  35 
to  180  and  the  acidity  increasing  from  0.002  per  cent,  to  0.298  per 
cent. ;  simultaneously,  the  viscosity  increased  about  20  per  cent. 
A  brownish  brittle  deposit  with  a  lustrous  fracture  developed 
throughout  this  system  having  the  following  composition: 

Per  cent. 

Water ..  24  ..2 

Oil 17.2 

Volatile  matter  insoluble  in  petroleum  spirit. . .  52.0 

Ash,  chiefly  iron  oxides 4.3 

Petroleum  acids ...;•;....... 2 . 3  as  SO3. 

CURTISS  VERTICAL  TURBINES 

These  turbines  are  chiefly  found  in  the  United  States,  only  a 
few  having  been  installed  in  England.  They  operate  electric 
generators  and  are  made  in  sizes  from  500  K.W.  to  20,000  K.W., 
the  corresponding  speeds  ranging  from  800  R.P.M.  down  to 
720  R.P.M.  The  revolving  parts  are  supported  by  a  combined 
step-and-guide  bearing  and  by  upper  and  middle  guide  bearings. 
The  middle  bearing  may  be  left  out  with  smaller  machines  where 
the  turbine  shaft  is  in  one  piece. 

The  step  bearing  is  shown  in  Fig.  79  and  consists  of  two  cast- 
iron  blocks,  one  carried  by  the  end  of  the  shaft  and  the  other 
held  firmly  in  a  horizontarposition,  and  so  arranged  that  it  can 


STEAM  TURBINES 


231 


bo  adjusted  up  and  down  by  a  powerful  screw.     The  lower  block 

is  recessed  to  about  half  its  diameter,  and  into  this  recess  oil  is 
forced  with  sufficient  pressure  to  balance  the  weight  of  the  whole 
revolving  element;  there  are  of  course  no  oil  grooves.  The 
amount  of  oil  required  is  small,  from  1J£  gallons  per  minute  for  a 
500-K.W.  machine  to  about  6  gallons  per  minute  for  an  8000-K.W. 
machine.  The  oil,  after  passing  between  the  blocks  of  the  step 
bearing,  wells  upwards,  lubricates  a  guide  bearing  supported 
by  the  same  casting  and  leaves  through  oil  drain  (1). 


FIG.   79. — Cuftiss  step  bearing. 

A  -carbon  packing,  prevented  from  rotation,  and  consisting  of 
two  sections  of  rings,  each  section  comprising  two  rings  made  up 
from  three  segments,  is  fitted  above  the  oil  thrower  (2),  and,  in 
order  that  no  oil  or  air  shall  enter  the  turbine  chamber  above  the 
packing,  a  low  steam  pressure  is  maintained  between  the  two 
sections  of  the  packing,  just  sufficient  so  that  vapor  is  visible 
at  the  outlet  of  drain  pipe  («3).  If  the  flow  of  oil  into  the  bearing 
is  too  great,  the  oil  overflows  into  drain  (3)  mixing  with  the  steam; 
the  mixture  should  be  drained  into  a  separate  tank  with  baffle 
plates,  in  which  the  water  is  held  back;  the  recovered  oil  may  be 
allowed  to  enter  the  main  oil  system  when  entirely  freed  from 
water. 


232 


PRACTICE  OF  LUBRICATION 


c 


The  oil  pressure  required  for  the  step  bearing  is  slightly  higher 
than  the  bearing  pressure,  ranging  from  300  to  800  Ib.  per  square 
inch,  thus  producing  perfect  oil  film  lubrication*.  To  start  lu- 
brication a  pressure  25  per  cent,  greater  than  the  normal  running- 
pressure  is  needed.  The  film  thickness  depends  upon  the  flow 
of  oil,  ranging  usually  from  0.003  inch  to  0.006  inch. 

In  some  designs  a  powerful  brake  bearing  is  provided  which  can 
be  operated  from  the  outside,  and  can  be  used  to  take  the  whole 
weight  of  the  revolving  part  in  case  the  step  bearing  support 
should  fail.  In  ordinary  operation  the  shoes  of  this  brake  will  be 
set  about  0.01  inch  below  the  brake  ring.  It  is  thus  in  a  position 

to  receive  the  revolving  part  in  case  the 
step  bearing  support  should  fail. 
Another  and  more  important  feature  of 
this  brake  is  to  stop  the  machine  when 
it  is  desired  to  do  so.  A  5,000-K.W. 
machine  will  run  for  four  or  five  hours 
after  the  steam  has  been  shut  off, 
unless  a  brake  is  applied. 

In  some  cases  the  step  bearings  have 
been  operated  with  water  instead  of 
oil,  in  which  case  no  packing  is  neces- 
sary, the  water  being  allowed  to  pass 
up  into  the  turbine.  The  trouble  with 
water  is  that  it  causes  rusting  of  parts. 
When  accidentally  the  step  bearing  oil 
pressure  has  dropped  below  the  pressure 
required,  the  bearing  surface  immedi- 
ately cuts;  but  the  metal  is  removed 
very  slowly  and  lubrication  is  easily  re- 
FIG.  so.-Oil  pressure  baffler,  established  when  the  pressure  oil  flow 

is  restored.     Precautions  are,  however, 

taken  in  the  shape  of  accumulators  and  other  auxiliaries  necessary 
forjjthe  maintenance  of  a  flow  of  pressure  oil  to  the  step  bearing. 
The  guide  bearings  are  babbit  lined  sleeves,  with  a  clearance 
of  0.0005  inch  per  inch  shaft  diameter  for  the  lower  guide  bearing, 
and  twice  this  clearance  in  the  upper  and  middle  bearing.  They 
have  suitable  oil  grooves  to  ensure  good  oil  distribution ;  the  oil  is 
fed  at  the  rate  o?  0.5  to  1.5  gallons  per. minute  per  bearing  accord- 
ing to  size,  and  is  distributed  by  gravity  from  an  elevated  oil 
tank,  or  from  branch  pipes  from  the  main  pressure  system. 

In  the  latter  case  bafflers,  as  illustrated  in  Fig.  80  are  fitted 
to  reduce  the  oil  pressure.  The  oil  is  forced  to  pass  through  the 
narrow  spiral  passage  formed  by  the  thread  and  the  longer  the 


STEAM  TURBINES 


233 


passage  the  more  is  the  pressure  reduced.  These  bafflers  are 
also  placed  in  the  delivery  line  to  the  step  bearing  to  reduce  the 
pressure  and  also  to  reduce  the  intensity  of  the  pulsations  caused 


FKJ.  81. 


FIG.  82. 
FIGS.  81,  82. — Preventing  oil  spray  from  guide  bearings. 

by  the  reciprocating  main  oil  pump.     When  the  oil  leaves  the 
guide  bearings  it  is  thrown  off  into  oil  troughs,  large  drain  pipes 
guiding  the  oil  back  into  the  oil  reservoir. 
A  carbon  packing  is  also  fitted  between  the  middle  guide  bearing 


234  PRACTICE  OF  LUBRICATION 

and  the  turbine;  excessive  steam  admitted  to  this  packing  will 
get  up  and  mix  with  the  return  oil  from  the  middle  guide  bearing 
and  should  be  avoided. 

The  guide  bearings  may  cause  trouble  by  oil  throwing,  caused 
by  leaky  joints  (which  is  easily  remedied)  or  by  oil  spray  sucked 
out  from  the  bearings  by  the  draught  created  by  the  rotating 
parts.  Deflectors,  as  shown  page  164  may  also  be  adapted  for 
vertical  turbines,  but  the  disease  is  a  troublesome  one  to  cure. 
Possibly  the  oil  supply  is  too  great,  particularly  when  the  oil  is 
introduced  under  great  pressuie,  or  the  oil  troughs  may  have 
become  obstructed  by  dirt,  which  may  account  for  the  oil  getting 
into  the  generator;  they  should  therefore  be  kept  clean,  as  well  as 
the  oil  return  pipes.  If  oil  leaks  through  a  porous  casting,  a 
mixture  of  litharge  and  glycerin  applied- to  the  points  of  leakage 
is  said  to  be  a  remedy. 

To  stop  the  fine  oil  spray  being  carried  out  from  the  bearings, 
it  is  necessary  to  equalize  the  air  pressure  outside  and  within, 
as  shown  in  Figs.  81  and  82  for  an  upper  and  middle  guide  bearing 
respectively.  The  pipes  (1)  are  pressure  equalizing  pipes,  taken 
outside  to  a  point  where  there  is  no  suction,  and  in  addition  felt 
rings  are  fitted,  as  shown,  and  prove  very  effective  as  long  as 
they  are  not  worn  too  much.  The  arrangements  in  Figs.  81 
and  82  were  designed  by  E.  D.  Dickinson  of  the  General  Electric 
Company.  The  casings  are  made  of  sheet  iron  with  rivetted 
joints;  the  felts  are  fastened  by  means  of  metal  rings.  Where 
bolts  are  used  they  should  be  locked,  so  that  the  nuts  cannot  come 
undone  through  vibration. 

Oil  Distribution. — The  oil  is  distributed  under  pressure  to  the 
step  bearings  and  guide  bearings  as  described,  but  the  latter  are 
sometimes  fed  from  an  elevated  tank,  with  an  overflow  pipe  back 
to  the  oil  reservoir.  On  its  way  to  the  bearings  the  oil  pressure 
is  reduced  by  one  or  more  bafflers,  so  that  each  bearing  gets  the 
right  amount  of  oil.  The  oil  is  returned  by  gravity  from  the 
bearings  and  passes  a  filtration  and  cooling  system,  in  which  it 
is  freed  from  water,  dirt  and  other  impurities,  before  it  is  circu- 
lated afresh. 

The  oil  reservoirs  should  preferably  be  in  duplicate  and 
operated  alternate  days,  similar  to  the  "two  tank"  system 
(page  217). 

When  water  is  used  for  the  step  bearing,  the  oil  pumps  have 
to  supply  oil  only  for  the  upper  and  middle  bearings,  usually  by 
way  of  an  elevated  tank.  The  amount  of  oil  going  to  each 
bearing  is  regulated  by  small  control  valves  and  sight  feeds  in 
each  line. 


STEAM  TURBINES  235 

In  an  installation  of  one  or  two  units  of  the  same  capacity, 
two  high-pressure  steam-driven  pumps  supply  oil  to  the  step  bear- 
ings and  two  low-pressure  pumps  supply  the  upper  and  middle 
guide  bearings  and  an  accumulator  gear,  for  equalizing  variations 
in  pressure  caused  by  fluctuations  in  the  speed  of  the  pumps. 
These  accumulators  in  case  of  failure  of  pump  will  keep  the 
turbines  running  for  some  time  and  automatically  cause  reserve 
oil  pumps  to  come  into  action.  The  accumulators  may  be.  on 
the  principle  of  a  heavy  weight  which  is  raised  or  lowered  accord- 
ing to  the  amount  of  oil  " stored'7  in  the  accumulator.  Air 
chambers  have  also  been  used  as  pressure  accumulators  and  must 
be  absolutely  air  tight.  In  installations  of  three  units  of  the 
same  capacity  three  high-  and  three  low-pressure  pumps  are 
fitted,  two  sets  being  sufficient  to  supply  all  units. 

In  a  plant  comprising  two  or  more  units  the  starting  or 
stopping  of  a  unit  means  that  the  amount  of  oil  required  is 
altered;  the  alteration  in  oil  supply  is  automatically  brought 
about  by  influencing  the  speed  of  the  oil  pumps.  The  latter 
should  run  at  no  greater  speed  than  that  required  to  give  the 
necessary  oil  supply  plus  a  margin.  If  the  speed  is  greater, 
power  is  wasted,  and  an  excessive  oil  supply  may  cause  various 
kinds  of  trouble,  such  as  oil  throwing,  oil  overflow  into  packing 
drain  pipe,  excessive  churning  of  the  oil  in  the  pumps  (causing 
emulsification  when  water  is  present),  etc. 

The  number  of  gallons  of  oil  in  circulation  is  about  10  per 
cent,  of  the  rated  K.W.  capacity  for  turbines  of  4000  K.  W.  or  over, 
20  per  cent,  for  turbines  between  2000  K.W.  and  4000  K.W.  and  a 
still  higher  percentage  for  smaller  turbines,  being  200  gal.  for  a 
500-K.W.  unit. 

Oil. — The  step  bearing  lubrication  is  not  dependent  upon  the 
viscosity  of  the  oil;  the  shaft  floats  on  the  oil  film,  whether  the 
oil  is  thick  or  thin,  simply  because  the  oil  is  introduced  at  a 
sufficiently  high  pressure.  Some  "body"  is  however,  required 
for  lubricating  the  guide  bearings,  particularly  when  there  is  a 
tendency  to  vibration.  Very  low  viscosity  oils  were  at  one  time 
used  for  Curtiss  turbines,  but  any  leakage  is  accentuated  by 
their  use,  and  more  oil  spray  may  be  formed  in  the  bearings.  The 
oil  must,  of  course,  be  a  circulation  oil  in  order  to  separate  well 
from  water  and  withstand  oxidation.  Unless  the  conditions 
specially  call  for  a  more  viscous  oil,  Circulation  Oil  No.  1  should 
be  recommended  in  all  cases. 

SELECTION  OF  TURBINE  OILS 

For  satisfactory  lubrication  of  steam  turbines  only  three  oils 
are  required  having  approximately  the  following  specifications: 


236  PRACTICE  OF  LUBRICATION 

Circulation  Oil  No.  I.1— Neutral  Filtered  Oil. 

Specific  gravity 870 

Flash  point  open 395°F. 

Saybolt  viscosity  at  104°F 135" 

Saybolt  viscosity  at  140°F 70" 

Setting  point. '. 20-25°F. 

Circulation  Oil  No.  2.1 — Mixture  of  a  Neutral  Filtered  Oil  and  Filtered  Ci/l- 
inder  Stock. 

Specific  gravity 900 

Flash  point  open 410°F. 

Saybolt  viscosity  at  104°F 265" 

Saybolt  viscosity  at  140°F 120" 

Setting  point 35°-40°F. 

Circulation  Oil  No.  3  l — Mixture  of  a  Neutral  Filtered  Oil  and  Filtered  Cyl- 
inder Stock. 

Specific  gravity 900 

Flash  point  open 425°F. 

Saybolt  viscosity  at  104°F 500" 

Saybolt  viscosity  at  140°F '    200" 

Setting  point 35-40°F. 

1  All  circulation  oils  must  separate  rapidly  from  water,  and  only  a  trace 
of  sludge  must  be  produced  in  the  emulsification  test. 

LUBRICATION  CHART  NO.  4 
FOR  STEAM  TURBINES 

Land  Turbines. — Circulation  Oil  No.  1  is  suitable  for  the  great 
majority  of  land  turbines,  including  the  vertical  type  of  Curtiss 
turbines. 

During  the  last  ten  years  or  so,  turbine  guilders  have  gradually 
realized  the  importance  of  using  a  light  viscosity  oil  for  high  speed 
turbines  and  have  designed  the  lubricating  system  in  such  a 
manner  that  the  pump  pressure  required  to  operate  the  governor 
gear  can  be  obtained,  notwithstanding  the  use  of  a  low  viscosity 
oil. 

The  advantages  of  such  an  oil  as  compared  with  a  heavy 
viscosity  oil  are: 

Lower  frictional  losses  (i.e.,  low  bearing  temperature). 

Rapid  removal  of  heat  from  the  turbine  bearings. 

Rapid  cooling  of  the  oil  in  the  coolers. 

Quick  separation  from  water,  dirt  and  other  impurities. 

Longer  life  of  the  oil. 

Greater  freedom  from  trouble. 

When  Circulation  Oil  No.  1  is  not  viscous  enough  to  give  the 


STEAM  TURBINES  237 

pump  pressure  required  for  the  governor  gear;  Circulation  Oil 
No.  2  or  even  No.  3  (in  very  special  cases)  must  be  used. 

Marine  Turbines. — Marine  turbines  operate  at  lower  speeds 
than  land  turbines  and  with  higher  bearing  pressures.  A  heavier 
viscosity  oil  is  therefore  required  and  Circulation  Oil  No.  2  will 
generally  be  found  to  be  the  correct  grade. 

Geared  Turbines  (Land  and  Marine). — The  lubricating  system 
for  the  gears  should  preferably  be  separate  and  distinct  from  the 
lubricating  system  serving  the  turbine  bearings,  as  the  conditions 
of  service  are  entirely  different,  and  frequently  Circulation  Oil 
No.  3  will  be  found  best  for  the  turbine  gears.  Only  in  rare  cases 
will  this  oil  be  the  most  suitable  oil  for  the  turbine  bearings,  as 
its  use  frequently  will  mean: 

High  f rictional  losses  (i.e.,  high  bearing  temperatures). 
Slow  separation  from  water,  dirt  and  other  impurities. 
Rapid  oxidation  of  the  oil  and  the  development  of  objectionable  deposits 
in  the  circulation  system. 

For  turbine  bearings  in  geared  turbines,  when  the  lubricating 
system  is  separate  from  that  serving  the  gears,  a  lighter  viscosity 
oil,  either  Circulation  Oil  No.  1  or  No.  2  should  preferably  be 
used,  as  recommended  under  Land  and  Marine  Turbines. 


CHAPTER  XIV 

BEARING  LUBRICATION  OF  STATIONARY,  OPEN 
TYPE  STEAM  ENGINES 

The  parts  to  lubricate  are  the  main  bearings,  the  crank  pin, 
the  crosshead  and  guide,  the  eccentric  straps  and  sheaves,  the 
valve  motion  and  the  governor. 

Main  Bearings. — In  small  engines  these  bearings  are  syphon 
oiled;  in  larger  engines  they  are  ring  oiled  or  are  oiled  from  a 
circulation  oiling  system. 

Crank  Pin. — The  crank  pin  in  most  engines  is  oiled  by  the 
banjo  system,  the  oil  being  delivered  into  the  banjo  either  by 


FIG.  83C 


FIG.  83B 


FIG.  83. — Crosshead  arid  guide  lubrication. 


a  sight  feed  drop  oiler  or  by  a  pipe  from  the  circulation  oiling 
system. 

Crosshead  and  Guide.—- Lubrication  of  the  crosshead  and  guide 
may  be  accomplished  as  shown  in  Fig.  83  A.  Oiler  (1)  lubricates 
the  top  slipper;  oiler  (2)  supplies  the  crosshead,  and  the  oil  leav- 
ing these  points  finally  reaches  the  bottom  guide,  being  retained 
by  the  splash  guards  (3).  The  crosshead  pin  may  also  be  lubri- 
cated through  holes  drilled  as  shown  in  Fig.  835;  the  oiler  (4) 
feeds  oil  to  the  wiper  (5)  which  is  fixed  on  the  crosshead  and 
delivers  the  oil  to  the  crosshead  pin. 

The  lower  crosshead  slipper  is  preferably  fitted  with  a  comb 

238 


BEARING  LUBRICATION  OF  STEAM  ENGINES          239 

shown  in  detail  in  Fig.  83C,  which  touches  the  guide  with  a  slight 
pressure  and  assists  in  spreading  the  oil  all  over  the  guide;  this 
arrangement  is  also  used  to  advantage  on  vertical  engines. 

Fig.  83  shows  a  bored  guide,  which  is  now  commonly  used  for 
stationary  steam  engines  and  which  gives  greater  satisfaction 
than  flat  guides.  Great  accuracy  is  more  easily  obtained  when 
the  surfaces  can  be  bored  and  turned  than  when  they  have  to  be 
planed. 

In  the  best  constructions  the  lower  guide  is  drilled  so  that  oil 
from  the  end  wells  continuously  flows  along  the  horizontal  passages 
and  up  through  these  holes,  being  distributed  by  means  of  short 
transversal  oil  grooves.  In  the  absence  of  this  arrangement  Fig. 
84  shows  suitable  grooving  of  the  bottom  guide  shoe  and  cham- 
fered edges  at  either  end  instead  of  combs. 

There  is  a  growing  tendency  to  construct  stationary  steam 
engines,  whether  vertical  or  horizontal,  with  a  gravity  circulation 
oiling  system,  consisting  of  a  pump,  top  and  bottom  tank,  dis- 
tributing pipes,  return  pipes,  and  a  strainer  or  filter  in  the  circuit 
as  for  example,  the  filter  (Fig. 
215,  page  552).  This  system 
entails  many  advantages  over 
the  ordinary  method  of  dis- 
tribution, such  as  greater 
certainty  of  the  oil  reaching 
every  part  and  greater  ease  in 

11-  ,1  -i  i          FIG.  84. — Oil  grooving  of  bottom  guide 

controlling    the    oil    supply,  gho* 

greater  margin   of   safety  in 

operation,  lower  friction  brought  about  by  an  abundant  supply 
of  lower  viscosity  oil,  and  an  appreciable  reduction  in  oil  con- 
sumption, when  care  is  taken  to  avoid  leakage  throughout  the 
system.  The  oil  wastage  in  gallons  per  month  will  with  a  good 
system  range  between  1  per  cent,  and  2  per  cent,  of  the  engine 
horsepower. 

The  governor,  valve  motion,  etc.,  are  usually  hand  oiled,  but  in 
large  engines  small  sight-feed  drop  oilers  are  employed  for  the 
most  important  parts. 

Bearing  Oils. — The  bearing  oils  used  for  external  lubrication  of 
stationary  steam  engines  are  usually  straight  mineral  oils,  as  they 
come  in  contact  with  more  or  less  water  of  condensation  from  the 
glands,  which  would  emulsify  compounded  oils. 

For  the  crank  pins  and  main  bearings,  when  they  do  not  form 
part  of  a  circulation  system,  and  when  they  are  heavily  loaded  or 
in  bad  mechanical  condition,  compounded  engine  oils  are  some- 
times required  to  keep  them  "cool,"  such  as  one  of  the  marine 


240  PRACTICE  OF  LUBRICATION 

•  engine  oils  (page  258).  In  extreme  cases  c,iist,or  oil  has  been 
used  with  great  success,  but  its  use  should  be  discouraged  on 
account  of  its  tendency  to  gum.  Castor  oil  is  often  resorted  to 
in  case  of  trouble  and  is  allowed  to  remain  in  use  instead  of 
correcting  the  mechanical  defect  and  introducing  a  proper  grade 
of  engine  oil,  which  will  on  an  average  reduce  the  frictional 
temperature  50  per  cent.,  as  shown  in  the  following  example, 
which  is  typical. 

On  the  main  bearings  of  a  steam  engine  where  castor  oil  was 
fed  through  an  oil  circulation  system,  the  rise  in  temperature  of 
the  bearings  above  room  was  17°F.  By  gradually  introducing 
an  oil  like  marine  engine  oil  No.  1  (called  X)  the  frictional  tem- 
perature was  reduced  as  follows: 


Bearing 
temperature, 
°F. 

Room 
temperature, 

Frictional 
temperature, 
F 

*           '    *      '  t  *      .'  *  •".'»./  ? 

Pure  castor  oil  

".?.VJ         88 

71 

17 

90%  castor  +  10%  X 

86 

71 

15 

80%  castor  +  20%  X  
60%  castor  +  40%  X     . 

82 

.  .  .    i         86 

69 
75 

13 
11 

Pure  X  oil  

!         90 

82 

8 

This  shows  a  decrease  in  the  frictional  temperature  of  53  per 
cent.  In  changing  over  from  castor  oil,  or  any  other  vegetable 
or  animal  oil,  to  an  oil  largely  mineral  in  character,  it  is  necessary 
to  exercise  great  care  and  make  the  change  gradually,  as  the 
deposits  which  have  accumulated  from  such  oils  are  loosened,  and 
if  loosened  too  quickly,  cause  trouble.  The  deposits  when 
loosened  gradually  are  caught  in  the  strainers  of  the  oil  pump  and 
should  be  removed  as  they  appear. 

It  is  not  unusual  to  find  steam  cylinder  oil  in  use  on  guides  or 
mixed  with  the  engine  oil.  This  is  bad  practice  as  the  great 
viscosity  of  the  cylinder  oil  causes  great  friction  and  high  tem- 
peratures; it  would  be  better  to  introduce  a.  marine  engine  oil 
on  guides,  inclined  to  be  troublesome,  assuming  that  they  can- 
not be  made  to  run  cool  on  the  ordinary  engine  oil. 

On  very  large,  long  stroke  engines  with  open  guides  and  tail 
rod  supports,  the  engine  oil  may  be  so  wasteful  in  splashing  away 
that  the  use  of  cylinder  oil  may  be  justified.  The  difficulty  with 
splashing  from  crank  pins  in  long-stroke  engines  and  providing 
proper  splash  guards  has  in  some  cases  prompted  the  use  of  crank 
pin  grease,  usually  a  white  grease,  in  place  of  oil. 


BEARING  LUBRICATION  OF  STEAM  ENGINES 


241 


In  large  crank-pin  bearings  or  main  bearings  on  slow-speed 
engines,  whether  grease  or  oil  is  employed,  oil  grooves  are  some- 
times an  advantage  when  the  engine  always  runs  in  one  direction. 
Fig.  85  shows  the  proper  way  of  making  the  oil  grooves  in  the  four 
parts  of  a  main  bearing;  the  straight  oil  grooves  and  chamfered 
edges  collect  and  feed  the  oil  along  their  entire  length.  The 
bearing  pressure  is  constantly  squeezing  the  oil  from  the  centre 
toward  the  edges  of  the  brasses,  but  the  curved  grooves  help  to 
conduct  the  oil  back  towards  the  centre  of  the  bearing. 


FIG.  85.  —  Oil  grooving  a  main  bearing. 


When  grooving  bearings,  an  important  rule  is  to  groove  only 
one,  not  both,  of  the  surfaces,  and  the  grooving  should  preferably 
be  done  in  the  female  or  enveloping  surface;  for  example,  the 
bearing  surfaces  of  the  connecting  rod  brasses  are  grooved,  not 
(lie  crank  pin  itself.  (See  Fig.  22,  page  115.) 

As  exceptions  to  this  rule  note  the  grooves  in  Fig.  84  and  the 
distributing  oil  grooves  in  long  spindle  bearings  for  machine 
tools  (Fig.  122,  page  292). 


242 


PRACTICE  OF  LUBRICATION 


LUBRICATION  CHART  NO.  5 
FOR  STATIONARY  OPEN  TYPE  STEAM  ENGINES 


Circulation  oiling 
systems,  H.P. 


Drop  feed 
systems,  H.P. 


Bearing  oil  No.  21 ; .  .  . 

Bearing  oil  No.  3 

Bearing  oil  No.  4 

Bearing  oil  No.  5,  6 


Marine  engine  oil  Nos.  1  and  2. 


Below  250  Below  100 

250  to  400  100  to  250 

Above  400  250  to  500 

For    special    cases!  Above  500 

only. 

Only  to  be  used  where  bearings  are 
subjected  to  abnormal  pressures  or  are 
in  bad  condition  mechanically. 


F  r  Bearing  oils,  see  page  127. 


CHAPTER  XV 

BEARING  LUBRICATION  OF  HIGH-SPEED    ENCLOSED - 
TYPE  STEAM  ENGINES 

The  vertical,  high-speed,  enclosed  type  of  steam  engine  has 
been  much  developed  in  England,  the  engines  ranging  in  size 
from  10  H.P.  to  2,500  H.P.  with  corresponding  speeds  of  from 
800  r.p.m.  down  to  250  r.p.m. 

The  horizontal,  high-speed,  enclosed-type  steam  engine  has 
come  into  favor  in  America  for  small  powers.  Both  the  vertical 
and  horizontal  types  may  be  lubricated  by  the  force  feed 
circulation  system  or  the  splash  oiling  system. 

Force-feed  Circulation. — Fig.  86  illustrates  a  typical  force- 
feed  circulation  system.  The  oil  pump  (1)  sucks  the  oil  from 
the  oil  reservoir  and  delivers  it  at  from  5  to  15  Ib.  pressure  per 
square  inch  through  pipes  (2)  into  the  main  bearings.  The  crank 
shaft  is  hollow  and  the  oil  is  forced  from  the  main  bearings  into 
the  shaft,  and  through  oil  passages  into  the  eccentric  sheave  and 
crank  pins,  whence  it  reaches  the  crosshead  bearings  through 
passages  in  the  connecting  rods  or  tubes  attached  thereto.  The 
oil  leaving  the  crossheads  splashes  on  the  crosshead  guides  and 
drops  back  into  the  crank  chamber.  The  oil  then  flows  to  the 
oil  reservoir  and  re-enters  the  oil  pump  through  a  strainer,  thus 
completing  the  circuit.  In  large  engines  the  guides  are  fed  with 
a  direct  supply  of  oil  from  the  main  distributing  pipe. 

An  adjustable  oil  relief  valve  (not  shown)  is  fitted,  which 
allows  a  portion  of  the  oil  to  overflow  back  into  the  oil  reservoir. 
In  this  way  the  oil  pressure  may  be  adjusted  within  certain 
limits.  The  oil  pump  should  be  of  ample  capacity,  so  that  the 
pump  pressure,  by  means  of  the  adjustable  relief  valve,  can  be 
kept  at  any  desired  point.  Too  small  an  oil  pump  or  slack 
bearings  decrease  the  oil  pressure,  or  make  it  necessary  to  use 
exceedingly  viscous  oils,  which  result  in  unnecessarily  high 
friction  losses. 

The  oil  pump  should  be  placed  with  its  suction  strainer  elevated 
to  leave  room  below  for  water  to  accumulate.  Otherwise  water 
is  drawn  with  the  oil  into  the  pump  and  forced  through  the  bear- 
ings, tending  to  emulsify  the  oil.  Water  gets  into  the  crank 
chamber,  owing  to  the  presence  of  ill-fitting  glands  or  " scored" 

243 


244 


PRACTICE  OF  LUBRICATION 


rods.  Where  the  rods  enter  the  crank  chamber  top,  scrapers 
are  preferable  to  glands  with  soft  packing.  The  oil  which  is 
carried  up  from  the  crank  chamber  and  scraped  off,  together  with 
the  water,  should  be  drained  to  an  oil  separator  outside  the 
crank  chamber  or  treated  in  a  steam  heated  settling  tank  to 
recover  as  much  oil  as  possible. 


FIG.  86. — Force-feed-circulation. 

Metallic  packings  are  preferable  to  soft  packing  in  these 
engines,  as  there  is  less  danger  of  " scoring"  the  rods  than  with 
soft  packing,  which  is  easily  screwed  up  too  tight.  Once  a  rod 
is  scored,  it  is  impossible  to  prevent  water  traveling  through  the 
"ridges"  down  into  the  crank  chamber. 


BEARING  LUBRICATION  OF  STEAM  ENGINES 


245 


Slightly  superheated  steam  is  an  advantage,  as  less  condensa- 
tion occurs  in  the  cylinders,  therefore  less  water  finds  its  way 
through  the  glands. 

The  crank  chamber  should  be  systematically  drained  at  suit- 
able intervals. 

A  drain  cock  of  preferably  not  less  than  \Y^  inch  bore  should  be 
fitted  at  the  lowest  point  in  the  crank  chamber,  and  if  the  water 
can  be  drained  off  while  the  engine  is  running,  this  should  be 
done  at  frequent  intervals.  Where  the  draining  cannot  be  ac- 
complished while  the  engine  is  running,  it  should  be  done  before 
starting  up,  every  time  the  engine  has  had  a  rest. 


FIG.  87, 


FIG.  88. 


Oil  and  water  separator. 


When  the  engine  is  supplied  with  wet  steam,  it  is  difficult  to 
prevent  an  excessive  amount  of  water  getting  into  the  crank 
chamber,  unless  the  rods  and  oil  scrapers  are  in  perfect  condition. 
When  this  is  not  the  case  the  piston  and  valve  rods  are  constantly 
splashed  with  oil  which  is  carried  up  through  the  scrapers.  Ac- 
cordingly, a  large  amount  of  a  mixture  of  oil  and  water  is  con- 
stantly scraped  off. 

Some  engines  have  holes  in  the  crank  chamber  top  which  allow 
the  water  and  oil  to  drain  straight  into  the  crank  chamber;  obvi- 
ously this  is  bad  practice.  Other  engines  have  an  automatic 
separator,  as  shown,  mounted  on  the  engine  in  Fig.  87  and  in 


246 


PRACTICE  OF  LUBRICATION 


detail  in  Fig.  88.  The  drain  pipe  (1)  from  the  crank  chamber 
top  enters  the  separator  at  the  side,  the  oil  rises  to  the  surface 
and  overflows  through  the  adjustable  pipe  (2)  back  into  the 
crank  chamber;  the  water  flows  below  a  baffle  and  leaves  the 
separator  through  the  drain  pipe  (3). 

As  to  the  water  which  drains  into  the  crank  chamber,  Fig.  89 
shows  a  useful  arrangement.  From  the  lowest  point  in  the  crank 
chamber,  whether  this  be  at  the  end  or  in  the  middle,  a  pipe  ( 1) 
is  connected  to  a  tank  (2)  which  acts  in  very  much  the  same 
way  as  the  " water  leg"  for  turbines.  Once  water  gets  into  the 


O 


FIG.  89.— Water  drainage  tank. 

tank,  it  cannot  re-enter  the  crank  chamber.  Accumulation  of 
water  should  be  drained  out  periodically. 

Every  plant  should  have  arrangements  for  treating  daily  a 
portion  of  the  oil  in  circulation,  to  free  it  from  water,  sludge  and  im- 
purities, and  so  maintain  its  vitality.  This  system  of  daily  treat- 
ment is  mentioned,  page  114  and  page  218  under  Steam  Turbines. 

In  large  engines  it  may  be  necessary  to  cool  the  oil  to  keep  its 
temperature  below  140°F. ;  a  cooling  coil  made  of  seamless  tube 
immersed,  in  the  oil  reservoir  is  usually  all  that  is  required. 
Practically  all  that  is  said  regarding  oil  in  connection  with  steam 
turbines,  applies  also  to  force  lubrication  steam  engines  and  will 
therefore  not  be  repeated  here. 


BEARING  LUBRICATION  OF  STEAM  ENGINES 


247 


The  oil  pressure  gauge  should  be  watched  regularly.  If  the 
oil  pressure  gradually  declines,  the  cause  may  be :  bearings  requir- 
ing adjustment,  emulsification  of  the  oil,  or  choking  of  the  filter. 

Some  engines  have  double  strainers  so  arranged  that  either 
can  be  removed  for  cleaning  without  disturbing  the  action  of  the 
oil  pump.  It  is  of  great  importance  that  the  strainers  be  kept 
clean  and  free  from  sludge  or  dirt. 

In  horizontal  engines  it  is  difficult  to  prevent  oil  from  splashing 
onto  the  piston  rod  and  getting  into  the  piston  rod  packing; 
with  saturated  steam  this  is  not  a  serious  matter,  but  with  super- 
heated steam  the  oil  carbonizes  in  the  packing.  Fig.  90  shows  a 
special  scraper  gland  fitted  round  the  piston  rod  and  fixed  in  a 
partition.  This  arrangement  is  used  in  some  large  Uniflow 
engines  and  has  proved  very  effective. 


1  Scraper  Gland 

2  Partition 

3  Piston  Rod 


FIG.  90. — Piston  rod  scraper  gland.     . 

Mutton  cloths  should  be  used  for  wiping  the  crank  chamber 
when  cleaning,  not  cotton  waste,  which  often  will  cause  trouble, 
as  the  fluffy  fibres  stick  to  the  surfaces,  are  afterwards  carried 
with  the  oil  to  the  pump,  and  may  choke  the  strainers. 

The  advantages  of  forced  lubrication  over  the  ordinary  me- 
thods are  many.  The  lubrication  is  entirely  self-contained.  The 
engines,  with  correct  bearing  adjustment  and  oil  pressure,  operate 
noiselessly  and  will  run  for  years,  practically  without  wear,  due 
to  the  perfect  film  formation.  As  the  engines  are  double-acting 
the  relaxation  of  pressure  on  the  upstroke  of  the  pistons  gives 
the  oil  a  chance  to  force  itself  thoroughly  in  between  the  rubbing 
surfaces,  forming  an  excellent  cushion  for  the  next  stroke.  In 
fact,  engines  may  be  run  with  the  bearings  rather  slack  and  yet 
without  noise;  there  is  not  sufficient  time  during  a  single  stroke 


248  PRACTICE  OF  LUBRICATION 

to  squeeze  the  oil  film  out,  particularly  if  the  oil  has  a  high  visco- 
sity. If  an  engine  uses  an  oil  too  low  in  viscosity  it  is  inclined  to 
run  noisily  and  the  oil  in  circulation  becomes  very  warm;  the 
introduction  of  the  correct  viscosity  oil  will  reduce  the  tempera- 
ture and  give  a  sweeter  running  engine. 

It  is  in  the  author's  opinion  good  practice  to  run  with  rather 
small  bearing  clearances  and  low  viscosity  oils;  such  oils  give 
less  friction,  lower  temperatures,  separate  more  easily  from  water, 
etc.,  and  last  longer  than  viscous  oils. 

•Force  feed  circulation,  when  properly  arranged,  is  a  very  eco- 
nomic oiling  system;  the  consumption  of  crank  chamber  oil 
ranges  from  .05  to  3.0  grams  per  B.H.P.  hour,  the  normal  aver- 
age being  1.0  gr.  per  B.H.P.  hour.  The  consumption  is  highest 
for  smaller  engines  and  when  a  great  deal  of  water  gets  into 
the  oil. 

Grades  of  Oil. — The  same  oils  as  are  used  for  steam  turbines 
should  also  be  used  for  forced  lubrication  steam  engines,  and  for 
normal  conditions  the  oils  may  be  recommended  as  follows : 

LUBRICATION  CHART  NO.  6 
FOR  FORCED  LUBRICATION  STEAM  ENGINES 

Circulation  Oil  No.  I1    For  engines  below  150  H.P. 
Circulation  Oil  No.  2     For  engines  from  150  H.P.  to  400  H.P. 
Circulation  Oil  No.  3     For  engines  above  400  H.P. 

NOTE. — Certain  makes  of  engines  operate  with  unusually  large  bearing 
clearances;  others  have  unusually  stout  connections  between  the  cylinders 
and  the  ciank  chamber,  so  that  a  large  amount  of  heat  is  carried  down 
from  the  cylinders  into  the  crank  chamber.  In  either  case  Circulation 
Oil  No.  2  must  be  used  for  engines  below  250  H.P.  and  Circulation  Oil 
No.  3  for  engine*  above  250  H.P. 

Splash  Oiling. — On  account  of  its  simplicity  and  low  cost  this 
system  is  used  to  some  extent  on  small  horizontal  engines  of 
American  make,  but  it  is  chiefly  used  for  vertical  single-acting 
engines,  like  the  Westinghouse  Engine  (U.  S.  A.)  and  the  Willans 
Central  Valve  Engine  (England),  the  former  being  made  in  all 
sizes  up  to  200  H.P.,  the  latter  in  sizes  up  to  1,500  H.P.  Splash 
oiling  is  rarely  used  for  vertical  double-acting  engines. 

The  crank  chamber  is  rilled  with  water  and  oil  to  a  level  about 
%  inch  below  the  underside  of  the  crank  shaft.  The  cranks  dip 
into  the  bath  and  splash  the  oil  to  the  crank  shaft  bearings,  crank 
pins,  eccentrics  and  pistons.  When  the  engine  is  to  be  started 
with  a  new  "bath"  after  the  chamber  is  thoroughly  cleaned, 
the  water  for  the  bath  must  be  rain-water  or  condensed  water. 
On  no  account  should  hard  water  be  used  or  water  from  a 
1  For  Circulation  oils,  see  page  236. 


HEARING  LUBRICATION  OF  STEAM  ENGINES 


240 


source  suspected  of  containing  acid,  chemicals  or  other  oils. 
When  the  water  has  been  poured  in  warm  (13()°F.)  the  right 
quantity  of  oil  can  be  added,  usually  a  layer  from  J£  inch  to  J£ 
inch  thick  which  equals  from  3  per  cent,  to  6  per  cent,  of  the 
volume  of  water  in  the  bath. 

The  engine  is  now  run  slowly  at  light  or  no  load,  until  the  bath 
gets  well  emulsified ;  first  then  should  the  full  load  be  put  on,  and 
only  after  examining  the  bath.  For  this  purpose  the  engine  is 
stopped  and  one  of  the  doors  removed;  the  oil  will  now  be  seen 
covering  the  surface,  and  after  the  surface  is  stirred  with  a  stick, 
the  water  underneath  must  appear  milky,  yellowish  white.  If 


i     i      i      i      i     i      i      i 

FIG.  91. — Water  overflow  arrangement. 

after  being  stirred  the  oil  flows  quickly  together  in  a  thick  film, 
there  is  too  much  oil  in  the  bath;  if  it  only  closes  over  the  water 
with  difficulty,  more  oil  must  be  added. 

During  operation  of  the  engine  more  or  less  water  from  the 
cylinders  (condensation),  particularly  with  wet  steam  conditions, 
finds  its  way  into  the  crank  chamber  and  the  level  of  the  bath 
rises.  An  automatic  overflow  should  therefore  be  fitted,  other- 
wise the  oil  overflows  through  the  end  bearings,  and  the  engine 
may,  run  short  of  oil.  Fig.  91  shows  such  an  overflow  arrange- 
ment, which  will  be  readily  understood.  When  the  level  (1) 
rises,  water  from  a  quiet  corner  in  the  bath  enters  the  inlet  to  the 


250 


PRACTICE  OF  LUBRICATION 


FIG. 


overflow  pipe  (2),  and  only  the  small  amount  of  emulsified  oil 
carried  away  with  the  water  is  lost.  Any  oil  carried  in  suspension 
will  be  retained  by  the  oil  separator  (3)  and  can  be  returned  to 
the  bath  through  the  vent  pipe  fitted  higher  up  on  the  crank 
chamber,  together  with  the  daily  or  weekly 
"make  up"  for  loss  in  oil. 

In  the  Westinghouse  engines  the  "make 
up"  oil  is  fed  through  oil  cups  to  the  main 
bearings,  and  leaving  these  reaches  the 
bath. 

When  superheated  steam  is  used,  and 
no  condensation  reaches  the  bath,  some 
water  will  evaporate  and  it  may  be  neces- 
sary to  add  condensed  water  to  the  bath 
to  keep  up  the  level.  In  such  cases  the 
crank  case  oil  consumption  with  a  good 
quality  oil  becomes  exceedingly  low. 
Consumptions  as  low  as  1  pint  per  24 
hours  for  a  1000  H.P.  Willans  engine  are 
on  record. 

The  greater  the  stream  of  water  leav- 
92.  — Willans  oil  ing  the  overflow  (4),  the  greater  the  oil 
consumption,  but  under  reasonably  good 

conditions,  a  consumption  of  0.5-3.0  pints  per  24  hours,  accord- 
ing to  the  size  of  engine,  will  prove  ample. 

There  are,  however,  special  sources  of  oil  loss,  such  as  loss 
through  end  bearings  or  past  the  pistons. 
Fig.  92  shows  the  oil  thrower  arrange- 
ment of  a  Willans  engine.  Any  lubri- 
cant reaching  the  oil  thrower  (1)  is  re- 
turned to  the  bath  through  the  passage 
shown.  Leakage  may  occur  if  the 
thrower  is  too  far  away  from  the  cover 
(2);  drops  of  oil  are  ordinarily  caught 
between  the  edge  of  the  thrower  and  the 
bevelled  edge  on  the  cover,  but  if  the 
space  is  too  great  oil  may  get  past,  with- 
out touching  the  thrower.  When  the 
oil  has  got  past  this  point  it  may  either 
leak  down  the  outside  of  the  cover  or  pass  along  the  shaft.  To 
prevent  the  latter  trouble,  the  clearance  between  the  shaft  and 
the  cover  must  be  sufficient  so  that  drops  of  oil  may  exist  on  one 
surface  without  touching  the  other. 

Leakage  of  oil  may  also  be  due  to  the  overflow,  being  choked 


FIG. 


93.— Willans    stuffing 
box. 


BEARING  LUBRICATION  OF  STEAM  ENGINES          251 

with  emulsified  clots  of  oil,  cotton  waste,  etc.  In  that  case  the 
bath  level  rises,  the  oil  finally  overflows  through  the  bearings,  and 
getting  caught  by  the  rim  of  the  flywheel  is  thrown  into  the  engine 
room  in  the  vicinity  of  the  flywheel. 

With  large  shaft  diameters  the  arrangement  shown  in  Fig.  92 
is  not  always  satisfactory  and  a  proper  gland  may  be  provided, 
with  very  soft  packing,  which  must  be  tightened  up  very  gently 
to  prevent  " grooving"  of  the  shaft.  To  avoid  s'uch  wear  tak- 
ing place  on  the  shaft  itself,  a  bushing  is  provided  as  shown  in 
Fig.  93. 

When  the  piston  rings  in  a  Westinghouse  engine  are  in  bad 
condition,  the  oil  splash  from  the  crank  chamber  will  get  drawn 
past  the  low-pressure  pistons  in  particular,  and  is  exhausted 
with  the  steam.  The  quality  of  the  oil  has  nothing  to  do  with 
this  trouble,  and  the  only  remedy  is  to  put  the  rings  in  order; 
rounding  the  upper  edges  of  the  rings  is  always  a  good  precaution, 
as  on  the  up-stroke  the  rings  will  ride  on  the  oil  film,  and  on  the 
down-stroke  scrape  off  excess  oil. 

Temperature. — The  presence  of  water  in  the  bath  ensures  that 
the  bearings  shall  not  reach  a  temperature  higher  than  212°F.,  but 
for  normal  running  it  is  preferable  to  keep  the  temperature  much 
lower,  say  120°F.  to  140°F.,  after  two  or  three  hours'  run. 

With  condensing  engines  this  temperature  is  rarely  exceeded, 
but  with  non-condensing  engines  the  greater  amount  of  heat 
from  the  cylinders  often  makes  the  bath  uncomfortably  hot; 
a  simple  arrangement  of  cooling  pipes  should  then  be  fitted,  and 
the  boiler  feed  water  may  be  used  as  cooling  water  on  its  way  to 
the  feed  pump.  Approximately  25  per  cent,  of  the  feed  water 
will  suffice  to  keep  the  bath  reasonably  cool. 

There  should  preferably  be  no  joints  in  the  cooling  coils  inside 
the  crank  chamber  to  avoid  leakage,  as  if  the  water  is  hard  or 
contains  acid,  chemicals  or  other  impurities,  a  leakage  into  the 
bath  may  destroy  the  oil.  For  similar  reason  cooling  waters 
should  be  avoided  which  are  liable  to  attack  the  cooling  coils, 
as  even  pin  holes  will  allow  a  great  deal  of  water  to  leak  in. 

Oils. — If  the  bath  were  made  with  oil  only  the  bath  temperature 
would  quickly  rise,  owing  to  the  large  amount  of  heat  developed 
by  fluid  friction  in  the  bearings  and  by  the  splashing  of  the  cranks 
through  the  viscous  oil.  When  the  bath  contains  only  a  few  per 
cent,  of  oil,  the  viscosity  of  the  emulsion  is  practically  the  same 
as  for  water  alone.  This  was  shown  by  K.  Beck  of  Leipzig,  and 
reported  in  Zeitschrift  fur  Physikalische  Chemie,  Vol.  LVIII;  the 
viscosity,  taken  by  an  Ostwald  viscometer,  of  a  10  per  cent, 
mixture  of  castor  oil  and  water  was  only  a  little  over  1  per  cent. 


252  PRACTICE  OF  LUBRICATION 

greater  than  the  viscosity  of  pure  water.  It  is  rather  curious 
that  even  with  fairly  high  bearing  pressures  the  water  emulsion 
is  capable  of  furnishing  adequate  lubrication.  The  explanation 
is  probably  that  little  particles  of  emulsified  oil,  or  of  oil  in  sus- 
pension, attach  themselves  to  the  rubbing  surfaces  and  form  a 
coating  which  prevents  metallic  contact;  and  the  friction  is  very 
low  because  of  the  low  viscosity  of  the  emulsion,  which  forms 
the  lubricating  film. 

In  the  early  days  castor  oil  was  the  favorite  lubricant,  but  it 
has  several  drawbacks;  it  becomes  acid  and  gummy,  due  to  oxida- 
tion, as  it  is  intimately  mixed  with  the  hot  air  in  the  crank  cham- 
ber. While  therefore  castor  oil  produces  excellent  lubrication  and 
a  rich  emulsion  it  often  leads  to  corrosion  of  the  surfaces  and  a 
sticky  deposit  accumulates  on  the  connecting  rods,  etc.  The 
consumption  of  castor  oil  is  comparatively  large,  as  the  water 
leaving  through  the  overflow  is  heavily  charged  with  emulsified 
castor  oil.  Castor  oil  is  now  seldom  used;  the  same  oil  is  used  in 
the  bath  as  in  the  steam  cylinders  and  valves. 

In  America  straight  mineral  dark  cylinder  oils  are  generally 
used  and  while  they  give  a  moderate  degree  of  satisfaction  under 
the  best  conditions,  the  results  are  not  at  all  good  when  the 
engines  employ  wet  steam  or  when  certain  hard  limy  boiler  feed 
waters  are  used.  The  emulsion,  which  is  always  poor  with  a 
straight  mineral  oil,  breaks  down  under  these  latter  conditions, 
resulting  in  high  friction  and  wear.  If  the  American  users  of  the 
Westinghouse  type  of  engine  knew  the  results  which  are  obtained 
by  the  use  of  lightly  compounded  filtered  cylinder  oils,  the  dark 
"Virginia"  and  similar  oils  now  used  straight  would  soon  be  dis- 
placed by  better  oils. 

Dark  cylinder  oils,  whether  straight  mineral  or  compounded, 
are  inclined  to  become  thick  and  livery,  particularly  if  there  is 
too  much  oil  in  the  bath.  In  large  engines,  where  the  conditions 
are  usually  less  trying  than  in  small  engines,  dark  compounded 
cylinder  oils  may,  however,  give  good  results,  but  in  smaller 
engines,  filtered  cylinder  oils  suitabty  compounded  with  fixed  oil 
are  much  to  be  preferred.  When  the  steam  is  wet  (boilers  prim- 
ing) and  boiler  impurities  are  carried  into  the  engine,  some  will 
reach  the  bath  and  will  tend  to  thicken  the  oil.  It  is  under  these 
conditions  that  dark  cylinder  oils  get  " livery,"  whereas  filtered 
cylinder  oils  are  very  little  affected,  even  if  there  is  rather  too 
much  oil  in  the  bath.  Filtered  cylinder  oils  thus  give  a  much 
greater  margin  of  safety  and  prove  more  economical  and  more 
efficient  than  dark  oils.  It  is  a  mistake  to  use  a  large  per- 
centage of  fixed  oil;  4  per  cent,  to  6  per  cent,  is  all  that  is  re- 


BEARING  LUBRICATION  OF  STEAM  ENGINES          253 


quirecL     With  more  fixed  oil  the  emulsion  becomes  unnecessarily 
rich  and  more  oil  is  lost  through  the  'overflow. 

Small  engines  are  sometimes  lubricated  with  a  bath  of  circula- 
tion oil,  but  15  per  cent,  to  20  per  cent,  of  oil  is  then  required  as 
compared  with  3  per  cent,  to  6  per  cent,  when  cylinder  oil  is 
employed.  Certain  small  engines  have  the  bearings  more  or 
less  enclosed,  and  the  oil  holes  are  rather  small.  If  cylinder  oil 
were  used  in  the  bath,  small  clots  of  emulsified  oil  would  choke 
these  small  openings,  and  circulation  oils  must  therefore  be 
used  for  such  engines. 

Sticky  deposits  may  develop  on  the  rods,  etc.,  as  already  men- 
tioned, in  reference  to  castor  oil;  similar  black  deposits  may 
be  produced  with  cylinder  oils,  particularly  so  with  dark  oils, 
and  they  will  appear  on  the  rods  in  peculiar  patterns  or  streaks 
caused  by  the  motion  of  the  rods,  and  consist  of  water,  oil,  oxi- 
dized oil  (insoluble  in  petroleum  spirit)  and  a  few  per  cent,  of 
iron  and  iron  oxides  (wear).  The  cause  of  the  deposits  may  be 
inferior  mineral  base  in  the  oil  (presence  of  too  much  coloring  and 
bituminous  matter),  or  inferior  fixed  oil  (too  much  free  fatty 
acid) ;  or  again,  the  quality  of  the  oil  may  not  be  at  fault,  but  the 
temperature  of  the  bath  is  above  140°F.  which  is  a  critical  tem- 
perature as  far  as  oxidation  of  the  oil  is  concerned.  Shortage  of 
oil  in  the  bath  will  also  bring  about  deposits,  but  they  will  then 
be  found  rather  rich  in  metallic  contents,  indicating  excessive 
wear. 

LUBRICATION  CHART  NO.  7 

FOR  HIGH  SPEED,  ENCLOSED  TYPE  ENGINES,  EMPLOYING 
THE  SPLASH  OILING  SYSTEM 


Engine  description 


Small,  horizontal  engines,  oper- 
ating in  ordinary  engine  rooms .  . 

Small,  horizontal  engines,  as  em- 
ployed in  steam  motor  wagons .  . 


Vertical  engines,  up  to  50  H.  P .  .  . 
Vertical  engines,  up  to  300  H.P.  . 
Vertical  engines,  above  300  H.P. . 


Grade  of  oil 


Circulation  oil  No.  1  or  No  21 
Circulation  oil  No.  3  or  simi- 
lar oil  of  even   higher  vis- 
cosity. 

Circulation  oil  No.  2 

or 

Cylinder  oil  No.  2  F.L.C.- 
Cylinder  oil  No.  2  F.L.C. 
Cylinder  oil  No.  3  F.M.C. 

or 
Cylinder  oil  No.  3  D.M.C. 


Percentage 

of  oil  used 

in  bath 


100 


100 
15 

4  to  6 
4  to  6 
3  to  4 

3  to  4 


1  For  Circulation  oils,  see  page  236. 

2  For  Cylinder  oils,  see  Table  No.  19,  page  389. 


CHAPTER   XVI 
CRANK  CHAMBER  EXPLOSIONS 

In  many  modern  high  speed  engines,  whether  they  be  steam, 
gas,  petrol  or  Diesel  engines,  the  crank  chamber  is  filled  with  oil 
spray,  a  more  or  less  dense  mist  of  fine  oil  particles.  These 
engines  are  acknowledged  to  be  safe  and  reliable  in  operation,  as 
far  as  lubrication  is  concerned,  notwithstanding  what  is  probably 
a  fact,  that  most  of  them  when  running  would  explode  were  a 
spark  to  be  formed  inside  the  crank  chamber. 

It  is  a  well  known  fact  that  to  make  an  explosive  mixture 
with  air,  an  inflammable  gas  of  some  kind  is  not  essential.  Any 
sufficiently  inflammable  substance  in  the  form  of  fine  dust  will 
produce  this  effect  if  present  in  the  requisite  proportion,  as  for 
example  in  the  case  of -many  explosions  in  coal  mines.  A  mixture 
of  air  and  coal  dust  can  be  made  to  explode  when  the  coal  dust 
reaches  a  certain  percentage;  and  as  soon  as  a  spark  or  a  naked 
flame  is  formed  or  brought  within  the  danger  zone  an  explosion 
will  occur.  An  explosion  of  this  character  occurred  in  an  oil 
cake  mill,  the  air  being  heavily  laden  with  fine  seed  dust;  the 
mixture  was  fired  by  a  spark  from  a  dynamo  and  many  lives  were 
lost.  Another  explosion  occurred  in  a  flour  mill,  sparks  from  a 
hot  bearing  firing  the  mixture  of  air  and  flour  dust. 

Coming  back  to  the  enclosed  high  speed  engines,  it  is  obvious 
that  from  the  time  of  starting,  an  increasing  amount  of  oil  spray 
is  formed  due  to  the  smashing  action  of  the  moving  parts  on  the 
stream  of  oil  escaping  from  gudgeon  pins  or  crossheads  and 
crank  pins.  When  the  engine  has  been  running  for  some  time, 
the  air  will  contain  a  certain  constant  amount  of  "oil  mist"  in 
accordance  with  the  conditions  of  speed,  ventilation,  etc.,  of  that 
particular  engine.  In  very  large  engines,  as  for  example  large 
enclosed  type  marine  Diesel  engines,  it  is  doubtful  whether  they 
ever  contain  sufficient  oil  mist  to  be  capable  of  exploding;  but 
in  smaller  and  much  higher  speed  engines,  the  danger  of  explosion 
is  ever  present. 

In  1911  an  enclosed  steam  engine,  300  H.P.  with  force  feed 
circulation,  exploded  in  a  large  hosiery  factory.  On  a  Monday 
morning  the  engineer  went  to  the  engine  room,  started  the  engine 
and  left  the  power  house;  a  few  minutes  later  the  engine  exploded. 
This  is  what  happened: 

During  the  week-end  the  engineer  had  tightened  up  the  brasses 
on  the  low  pressure  crosshead,  and  on  Monday  morning  the 

254 


CRANK  CHAMBER  EXPLOSIONS  255 

engine  was  started  up  without  examination  as  to  whether  this 
bearing  had  been  tightened  up  too  much,  which  unfortunately  was 
the  case.  After  a  few  minutes  the  crosshead  got  hot;  the  heat 
spread  to  the  cast-iron  slippers,  which  work  vertically  in  circular 
guides  about  8  inches  diameter.  The  clearance  was  only  about 
0.01  inch  when  cold  and  0.002  or  0.003  inch  with  the  engine  warm ; 
consequently,  the  excessive  heat  conducted  from  the  crosshead 
pin  caused  the  slippers  to  expand  and  seize.  The  circular  guides 
broke  and  flying  sparks  from  the  slippers  fired  the  mixture  of  air 
and  atomized  oil  in  the  crank  chamber.  The  governor  casing 
blew  off,  the  opposite  wall  of  the  engine  room  fell  out,  while  one 
of  the  other  walls  was  moved  4J^  inches  and  the  roof  of  the  engine 
room  was  blown  away.  The  engineer  having  left  the  engine 
room,  nobody  was  killed. 

Another  disaster  took  place  on  a  British  battleship.  An 
enclosed  steam  engine  exploded  and  killed  a  number  of  men. 
The  papers  reported  that  the  explosion  was  due  to  carelessness 
on  the  part  of  one  of  the  men,  who  approached  the  engine  with 
a  naked  light  just  after  it  had  been  opened  and  the  inspection 
doors  removed,  so  that  the  crank  chamber  was  still  full  of  the 
mixture  of  atomized  oil  and  air. 

Similar  explosions  have  been  reported  in  connection  with 
Diesel  engines  installed  in  submarines  belonging  to  one  of  the 
large  Continental  powers,  and  in  several  cases  the  explosion  was 
due  to  sparks  in  the  crank  chamber  owing  to  one  of  the  pistons 
seizing.  This  would  seem  to  indicate  that  as  far  as  cylinder  lubri- 
cation is  concerned,  the  greatest  care  should  be  taken  in  designing 
the  lubricating  system,  and  in  using  such  oils  as  will  ensure  as 
safe  and  clean  lubrication  as  possible  of  the  pistons,  particularly 
so  in  the  case  of  Diesel  engines  for  naval  purposes,  where  high 
speed  and  short  connecting  rods  are  the  characteristic  features, 
owing  to  the  cramped  space  available  for  the  engines. 

Several  explosions  have  happened  in  the  past  with  enclosed 
high  speed  gas  engines,  due  to  exactly  similar  conditions,  namely, 
a  mixture  of  air  and  atomized  oil.  It  is  a  fact  worthy  of  note 
that  at  least  one  firm  of  engine  builders  in  England  now  ventilate 
their  enclosed  gas  engines  and  Diesel  engines  by  fitting  a  small 
fan  that  removes  from  the  crank  chamber  any  gases  that  may 
pass  the  pistons,  as  well  as  the  finest  oil  vapor,  thus  making  the 
possibility  of  an  explosion  very  remote  indeed. 

This  system  appears  to  be  particularly  desirable  for  high 
speed  naval  Diesel  engines  and  has  been  used  in  Continental 
submarines;  to  avoid  excessive  loss  of  oil,  the  fan  discharges 
through  a  separating  tank,  in  which  baffle  plates  cause  a  portion 
of  the  oil  to  " condense"  and  settle  out. 


CHAPTER  XVII 
BEARING  LUBRICATION  OF  MARINE   STEAM   ENGINES 

Hand  oiling  is  still  used,  the  practice  being  to  pour  oil  from  an 
oil  feeder  into  oil  cups,  say  during  four  to  eight  revolutions  of 
the  engine  every  half  hour.  The  bearings  get  flooded  with  oil 
after  each  oiling  and  thereafter  the  oil  film  is  gradually  squeezed 
out  and  lubrication  becomes  less  and  less  efficient  until  such  time 
as  the  bearings  are  oiled  again.  Obviously  this  method  is  both 
wasteful  and  inefficient. 

The  better  method  now  most  frequently  employed  is  to  have 
oil  cups  fitted  with  syphon  wicks  which  syphon  the  oil  from  the 
cups  and  deliver  it  into  oil  pipes  leading  to  the  various  bearings. 
Syphon  oil  boxes  are  fitted  near  the  tops  of  each  cylinder  and 
distribute  the  oil  through  feed  pipes  ending  in  "  wipers, "  which 
are  touched  by  oil  receiving  boxes  fixed  on  the  moving  parts,  at 
the  moment  these  boxes  reach  their  highest  positions;  the  oil  is 
finally  guided  to  the  various  points  through  pipes  fixed  to  the 
moving  parts. 

A  syphon  box  is  fitted  over  each  main  bearing  with  two  or 
more  oil  feeds  according  to  the  size  of  the  shaft;  from  these  boxes 
may  also  be  taken  oil  feeds  for  the  crank  pins,  when  the  latter 
are  arranged  for  " banjo"  oiling.  An  oil  box  is  fitted  for  each 
crosshead  guide,  and  a  comb  fitted  to  the  bottom  end  of  the  slipper 
dips  into  the  oil  well  and  qarries  the  oil  well  up  on  the  guide  which 
is  usually  water  cooled. 

The  oil  feeds  vary  with  changes  in  temperature,  the  oil  feeding 
more  quickly  when  warm,  due  to  its  lower  viscosity.  The  oil 
feed  is  much  dependent  on  the  oil  level  in  the  cups.  The  syphons 
feed  more  slowly  when  the  oil  level  is  low;  it  is  therefore  neces- 
sary to  keep  the  oil  level  as  uniform  as  possible  by  frequently 
replenishing  the  oil  cups. 

A  better  system  is  to  replenish  the  various  syphon  oil  cups  not 
by  hand  but  from  a  centrally-placed  oil  tank,  feeding  adjustable 
quantities  of  oil  through  the  feed  pipes,  each  of  these  having  a 
sight  feed  arrangement  by  which  the  oil  feed  can  be  ascertained 
going  to  the  corresponding  oil  cup.  If,  for  example,  one  feed 
pipe  is  feeding  60  drops  per  minute  to  one  of  the  oil  cups,  the 
latter  distributing  by  syphons  the  oil  to  several  points,  then  the 

256 


BEARING  LUBRICATION  OF  MARINE  STEAM  ENGINES     257 

oil  level  in  this  cup  will  quickly  adjust  itself  automatically  to 
such  a  level  that  the  oil  syphons  all  told  will  syphon  out  60  drops 
per  minute.  If  they  feed  more,  the  oil  level  will  gradually  de- 
crease until  a  point  is  reached  when  the  oil  feeds  all  told  amount 
to  60  drops  per  minute.  The  control  of  the  oil  feeds  from  the 
central  oil  tank  can  best  be  done  by  mechanically  operated  lubri- 
cators, which  start  and  stop  feeding  with  the  engine. 

Experience  has  proved  that  the  installation  of  such  a  central 
distributing  oil  tank,  preferably  in  connection  with  mechanically 
operated  lubricator  pumps,  will  save  from  40  per  cent,  to  60  per 
cent,  of  the  total  amount  of  oil  consumed  for  external  lubrication. 

There  is  always  a  greater  or  less  amount  of  condensed  steam 
finding  its  way  down  the  piston  and  valve  rods  and  dropping  all 
over  the  external  moving  parts,  and  in  case  of  a  hot  bearing  the 
cold  water  hose  is  frequently  applied.  Sometimes  a  small  trickle 
of  water  is  allowed  to  run  into  or  on  to  those  bearings  which  are 
inclined  to  run  rather  warm.  When  oils  pure  mineral  in  charac- 
ter are  used  the  water  will  displace  the  mineral  oil  and  the  bear- 
ings will  heat  and  may  seize. 

Marine  engine  oils  should  therefore  be  compounded  with  a 
suitable  percentage  of  good  quality  fixed  oil,  so  that  they  will 
saponify  freely  with  water  and  form  a  rich  and  creamy  lather. 
Good  quality  marine  oils,  while  they  combine  satisfactorily  with 
water,  will  give  more  efficient  and  more  economical  lubrication 
if  they  are  used  without  water.  The  oil  when  leaving  the  bear- 
ings, usually  in  a  more  or  less  emulsified  condition,  is  run  to  waste 
into  the  bilges,  it  being  impossible  to  recover  the  oil  from  the 
emulsified  waste  oil. 

Marine  engine  oils  should  contain  only  a  small  percentage  of 
fatty  acid,  say  less  than  0.4  per  cent,  in  terms  of  S03,  so  as  not  to 
cause  corrosion  or  pitting.  The  fixed  oil  should  not  produce  a 
disagreeable  odor  exposed  to  the  heat  in  the  engine  room,  nor 
should  the  fixed  oil  used  for  compounding  be  of  a  drying  nature, 
but  semi-drying  oils  like  rape  oil  will  give  good  service.  Castor 
oil  was  at  one  time  much  used  and  is  still  used  largely  in  the  East, 
but  is  expensive  when  used  alone.  It  can,  however,  be  mixed 
with  mineral  oil  in  the  presence  of  an  animal  oil,  say,  20  per  cent, 
castor,  6  per  cent,  lard  oil  and  74  per  cent,  heavy  viscosity  mineral 
oil,  preferably  Texas,  Russian  or  other  asphaltic  base  oil  to  get  a 
low  setting  point.  The  lower  the  setting  point  and  the  greater 
the  percentage  of  good  quality  fixed  oil  of  reasonably  low  cold 
test,  the  less  will  the  oil  be  affected  by  climatic  changes. 

The  bearings  of  large  marine  steam  engines  require  oils  of 
great  oiliness  to  give  the  necessary  margin  of  safety  under  the 

17 


258 


PRACTICE  OF  LUBRICATION 


severe  operating  conditions.  Pure  mineral  oils  of  the  requisite 
oiliness  do  exist,  but  they  are  so  viscous  that  they  will  not  syphon 
properly  and  feed  irregularly  owing  to  poor  cold  tests.  The 
admixture  of  fixed  oils  having  great  oiliness  is  therefore  dictated 
not  only  by  the  presence  of  water,  but  also  by  the  necessity  of 
keeping  the  cold  test  and  viscosity  of  the  finished  oil  reasonably 
low.  Blown  rape  oil,  blown  cod  oil  or  blown  whale  oil,  prefer- 
ably the  first  mentioned,  are  used  to  the  extent  of  10  per  cent,  to 
25  per  cent.,  the  fixed  oils  being  usually  blown  until  they  have 
a  viscosity  of  720"  to  1400"  Saybolt  at  210°F.  Such  very 
viscous  fixed  oils  raise  the  oiliness  and  the  viscosity  of  the  min- 
eral base  appreciably  without  unduly  raising  the  setting  point. 

In  Table  No.  9  are  given  typical  readings  of  three  marine 
engine  oils  which  will  serve  for  all  marine  purposes  where  com- 
pounded oils  are  needed.  The  important  figures  are  those  for 
viscosities,  cold  tests  and  compound;  the  figures  for  specific 
gravity  and  flash  point  are  of  little  consequence. 

Large  engines  and  vessels  navigating  in  hot  climates  need 
higher  viscosity  oils  than  smaller  engines  or  vessels  operating  in 
colder  climates,  but  only  practical  tests  extending  over*  a  period 
of  say  three  "months  can  decide  which  of  the  three  grades  should 
be  preferred  and  what  percentage  of  compound  it  should  contain. 
The  higher  viscosity  oils  are  usually  the  more  economical,  but 
they  may  be  unnecessarily  viscous  and  thus  waste  power  in 
creating  too  much  "oil  drag"  in  the  bearings. 

TABLE   No.  9 


Specific 
gravity 

Saybolt  viscosities  at 

Open 
flash 
point 

Cold 

test 

*Per  cent, 
of 
compound 

104°F. 

140°F. 

212°F. 

Marine  engine  oil  No.  1  .  . 
Marine  engine  oil  No.  2  .  . 
Marine  engine  oil  No.  3.  . 

.920 
.930 
.940 

450 

750 
1400 

190 
270 
340 

65 
75 

85 

400 
405 
410 

25 

2^o 

3%5 

10-20 
10-20 
15-25 

Forced  circulation  has  during  recent  years  made  great  progress 
in  naval  ships  both  in  Europe  and  the  United  States,  not  only 
for  steam  turbines  and  auxiliary  high  speed  enclosed  type 
steam  engines,  but  also  for  the  large  reciprocating  type  main 
engines  in  destroyers  and  other  craft. 

The  working  parts  including  the  crossheads  are  enclosed  in  an 
oil  tight  casing,  packed  glands  being  provided  for  the  piston  and 
valve  rods  to  prevent  too  much  water  getting  down  into  the  oil 
in  circulation.  Observation  windows  and  electric  lights  may  be 
fitted  to  watch  the  moving  parts.  The  oil  is  supplied  by  recipro- 


BEARING  LUBRICATION  OF  MARINE  STEAM  ENGINES    259 

eating  pumps  operated  by  the  engine  itself  or  independent 
thereof.  The  oil  may  be  forced  into  the  hollow  crankshaft,  holes 
being  drilled  radially  at  each  main  bearing,  crank  pin  and  ec- 
centric, the  oil  from  the  crank  pin  continuing  its  way  through  a 
tube  fitted  to  the  connecting  rod  into  the  crosshead  bearing, 
finally  reaching  the  crosshead  guides. 

The  oil  delivery  pipes  may  also  deliver  the  oil  into  the  main 
bearings  first  of  all,  the  oil  thence  reaching  the  hollow  crank  shaft, 
etc.,  as  is  customary  on  land  engines. 

The  oil  supply  system  is  frequently  made  in  duplicate. 

The  oil  collecting  in  the  oil  wells  is  pumped  away  by  indepen- 
dently operated  pumps,  fitted  with  suction  strainers,  the  oil 
being  delivered  through  a  filter  to  a  " settling  tank,"  finally 
reaching  the  storage  tanks  ready  to  be  circulated  afresh. 

Main  engines  fitted  with  forced  oil  circulation  have  been 
inspected  after  the  vessel  has  done  20,000  miles,  and  the  tool 
marks  in  the  white  metal  bearings  were  found  to  be  still  visible 
and  no  measurable  wear  had  taken  place. 

The  risks  of  accidents  due  to  hot  bearings  caused  by  in- 
sufficient oil  supply  are  practically  eliminated  by  this  system; 
there  is  a  great  saving  in  the  time  and  expense  which  was  required 
with  syphon  lubrication  in  rebabbitting,  adjusting  and  examining 
bearings  after  each  voyage.  The  cost  of  lubrication  is  also 
much  reduced  by  forced  oil  circulation  and  the  engines  operate 
much  more  quietly. 

Auxiliary  engines  which  are  now  frequently  fitted  with  a 
full  force  feed  circulation  system  should  preferably  have  the 
cylinders  raised  so  high  above  the  crank  chamber  top  that  no 
part  of  the  piston  and  valve  rods  entering  the  cylinder  or  valve 
glands  will  enter  the  scraper  glands  fitted  in  the  crank  chamber 
top.  If  this  be  arranged,  no  oil  from  the  crank  chamber  can 
possibly  enter  the  steam  cylinders,  which  is  important  with  a 
view  to  preventing  oil  from  reaching  the  boilers. 

The  oils  used  for  force  feed  circulation  systems  must  be  similar 
to  those  used  for  steam  turbines,  i.e.,  they  are  circulation  oils. 
Circulation  Oil  No.  2  is  used  on  most  small  auxiliary  high  speed 
engines,  Circulation  Oil  No.  3  on  large  slower  speed  engines,  and 
larger  auxiliary  high  speed  engines. 

One  might  ask  why  these  oils,  pure  mineral  in  character  and 
lower  in  viscosity  than  the  compounded  marine  engines  oils,  can 
replace  the  latter  and  with  such  great  success.  The  answer  is 
simply  that  the  oil  is  supplied  to  all  bearings  in  abundance,  not 
only  supplying  a  complete  lubricating  film,  but  also  continuously 
removing  frictional  heat  from  the  bearings,  which  therefore  run 


260 


PRACTICE  OF  LUBRICATION 


much  cooler.  The  bearings  do  not  get  contaminated  with  water, 
and  as  the  revolving  parts  practically  "float"  on  a  complete  oil 
film,  wear  is  practically  eliminated  and  the  results  are  excellent 
from  every  point  ,of  view. 

It  is  to  be  hoped  that  the  merchant  marine  will  take  advantage 
of  the  experience  gained  by  the  various  navies  with  force  feed 
circulation,  which  undoubtedly  is  very  superior  to  the  systems 
now  generally  employed. 

Thrust  Bearings. — Fig.  94  illustrates  the  horseshoe  type  of 
thrust  bearing  still  almost  universally  used  for  marine  steam 
engines.  The  collars  on  the  shaft  press  against  the  horseshoes, 
which  are  adjustable  in  a  fore  and  aft  direction  so  as  to  distribute 
the  load  more  or  less  evenly  between  them.  Changes  in  tem- 
perature difference  between  shaft  and  horseshoes  alter  the  distri- 
bution of  load  and  cause  heating  of  certain  collars  and  shoes, 
so  that  a  hot  thrust  is  by  no  means  uncommon,  in  fact,  the  thrust 


FIG.  94. — Horse  shoe  thrust  hearing. 

bearing  often  gives  the  engineers  more  trouble  than  any  other 
bearings  or  part  of  the  engine  room  machinery.  The  oil  is  fed 
by  syphons  from  the  top  and  led  into  oil  grooves  of  various 
" fancy"  patterns.  The  collars  are  often  arranged  to  dip  into 
the  oil  and  carry  the  oil  up  with  them.  The  oil  bath  is  sometimes 
fitted  with  a  cooling  coil,  but  it  is  more  effective  to  cool  the 
horseshoes  themselves,  which  is  often  done  in  large  and  important 
thrust  bearings.  (See  Fig.  95.) 

The  lubrication  is,  however,  always  poor,  as  the  centrifugal 
force  throws  the  oil  away  from  the  points  where  it  is  most  needed ; 
the  bearing  pressures  allowed  are  therefore  low,  usually  50-70  Ibs. 
per  square  inch,  with  a  mean  surface  speed  of  500  ft.  per  minute, 
but  with  the  best  cooling  arrangements  and  perfect  workmanship 
a  bearing  pressure  of  100  Ibs.  per  square  inch  and  a  mean  surface 
speed  of  600  ft.  per  minute  has  been  accomplished ;  and  in  other 
cases  a  pressure  of  60  Ibs.  per  square  inch  with  a  surface  speed 
of  800  ft.  per  minute.  The  friction  is  high,  often  consuming 
5  per  cent,  of  the  shaft  horsepower;  the  rubbing  surfaces  are 


BEARING  LUBRICATION  OF  MARINE  STEAM  ENGINES     2(51 

in  only  a  semi-lubricated  condition,  the  coefficient  of  friction 
being  approximately  .03. 

The  Michell  single  collar  thrust  bearing  (see  page  170)  will 
no  doubt  come  more  and  more  into  general  use,  not  only  for 
marine  turbines  but  also  for  marine  steam  engines,  as  with  a 
little  intelligent  attention  it  gives  no  trouble  whatsoever  and 
consumes  less  than  one-tenth  of  the  friction  ordinarily  wasted 
in  the  horseshoe  type  of  thrust  bearing. 

Stern  Tube  Lubrication. — A  large  majority  of  ships  are  fitted 
with  Lignum  Vitae  stern  tube  bearings,  the  propeller  shaft  being 
fitted  with  a  bronze  liner,  and  the  lignum  vitae  being  placed  as 
strips  2  inches  to  3  inches  wide  with  2  inch  spaces  between  the 
strips.  Salt  water  is  usually  the  only  lubricant  used  in  these 


3, 


FIG.  95. — Cooling  the  thrust. 

bearings,  but  occasionally  the  stern  tube  gland  is  fed  with  a 
Stauffer  grease  cup  through  which  a  suitable  grease  can  be  fed 
into  the  gland  with  a  view  to  reducing  the  considerable  amount 
of  friction  which  is  generated  here. 

Unquestionably  there  is  a  very  great  frictional  loss  in  the 
lignum  vitae  stern  tube  bearings,  and  the  only  way  to  reduce 
this  frictional  loss  is  to  fit  the  bearing  with  an  outer  gland  as  in 
the  case  of  the  Cederwall,  Vickers,  or  similar  type  of  packing. 
Thus  enclosed  the  lignum  vitae  can,  if  desired,  be  replaced  by 
proper  bearing  metal  and  in  any  case  the  stern  tube  bearing  can 
be  efficiently  lubricated  by  means  of  oil  or  thin  grease.  This 
means  a  great  saving  in  power  and  also  entails  the  advantage 
that  where  the  vessel  gets  into  shallow  waters,  as  is  the  case  with 
a  number  of  river  boats  or  coasting  steamers,  the  entrance  of  mud, 
sand  or  other  impurities  is  entirely  obviated,  thus  preventing 


262 


PRACTICE  OF  LUBRICATION 


trouble  and  giving  much  longer  life  to  the  stern  tube  bearing, 
the  wear  being  practically  eliminated. 

Another  advantage  is  that  galvanic  corrosion,  rusting  and 
pitting  of  the  shaft  cannot  take  place,  assuming  of  course  that 
the  lubricant  employed  is  of  reasonably  good  quality. 

An  arrangement  patented  by  Vickers  and  Sons,  Leeds,  is 
illustrated  in  Fig.  96  and  was  referred  to  in  " Engineering." 
They  write  as  follows : 

"This  appliance  was  fitted  to  two  twin-screw  hopper-barges  con- 
structed for  the  Clyde  Navigation  Trustees  by  Messrs.  Fleming  and 
Ferguson,  Limited,  of  Paisley,  in  1896.  After  running  two  years 
the  shafts  were  examined,  and  were  found  to  be  in  very  good  condi- 
tion. They  were  again  examined  quite  recently  after  three  years' 
continuous  work,  and  the  wear  was  found  to  be  less  than  ^2  in.  of 


1  Floating  Packings 

2  Elastic  Disc  Packing 

3  White  Metalled  Bushing 

4  Oil  Supply  from  Tank  above 

5  Oil  Feed  Pipe 

6  Oil  Overflow  Pipe 

7  Handpump  Oil    Supply 

8  Gland  with  Soft  Packing 


FIG.  96. — Vickers'  stern  tube  packing. 

the  total  diameter  of  the  shaft  in  the  bush,  so  that  it  was  not  con- 
sidered necessary  to  true  up  the  bushes.  When  one  remembers  the 
peculiar  gritty  nature  of  the  Clyde  water,  and  that  the  barges  are 
often  in  close  proximity  to  dredges  which  are  disturbing  the  bed  of 
the  river,  this  result  will  be  accepted  as  very  satisfactory.  The  section 
is  almost  self-explanatory.  It  will  be  seen  that  on  each  side  of  the 
floating  packing  there  are  two  packings ;  and  next  the  guard-ring  there 
are  elastic  discs  which  grasp  the  shaft  like  the  sleeve  of  a  diver's  jacket. 
The  inner  one  is  a  fine  elastic  woollen  felt,  and  the  outer  of  a  special 
composition  of  a  slightly  elastic  nature  which  is  unaffected  by  either 
sea  water  or  oil.  Incidentally,  the  application  of  oil  here  reduces  the 
friction,  and  as  the  friction  resistance  within  the  stern  tube  is  a  large 
proportion  of  the  total  friction  of  the  engine  and  shaft,  the  advantage 
is  very  considerable." 


BEARING  LUBRICATION  OF  MARINE  STEAM  ENGINES     263 

The  continuous  bronze  liners  now  often  fitted,  which  are 
carried  right  into  the  propeller  boss,  protect  the  shaft  from 
galvanic  corrosion,  but  do  not  prevent  the  entry  of  sand,  so  that 
whatever  system  of  lining  or  bushing  (cast  iron,  white  metal  or 
lignum  vitse)  is  employed,  many  advantages  are  always  obtained 
by  enclosing  the  stern  tube  and  having  a  proper  oiling  arrange- 
ment fitted. 


CHAPTER  XVIII 

RAILWAY  ROLLING  STOCK 

BEARING  LUBRICATION  OF  LOCOMOTIVES,  TENDERS  AND  CARS 

Axle  boxes. — Axle  boxes  are  termed  inside  or  outside  according 
to  whether  they  are  inside  or  outside  the  wheels.  Generally 
speaking,  tenders  and  cars  have  outside  axle  boxes  and  locomo- 
tives inside  boxes;  some  locomotives,  however,  have  the  wheels 
inside  the  frames  and  the  axleboxes  outside. 

Fig.  97  shows  an  outside  axle  box.  A  door  is  formed  in  the  front 
portion  of  the  box.  To  prevent  rain  water  from  entering  the 
box  through  the  joint,  the  box  may  project  above  the  door,  as 


FIG.  97. — Outside  axle  box.  . 

shown;  another  solution  is  to  have  attached  to  the  door  a  sheet 
metal  rain-guard  which  projects  over  the  top  of  the  box  (Fig.  98). 
For  the  same  reason  the  door  should  be  so  designed  as  to  prevent 
water  getting  in  at  the  sides  and  bottom.  At  the  wheelside  of 
the  box  is  a  dust  guard,  usually  made  of  wood,  in  two  halves, 
which  are  forced  gently  against  the  shaft  by  springs.  One  type 
of  dust  guard  has  oil  pads  fitted  in  little  recesses  in  both  halves 
which  are  made  of  lignum  vitse;  the  bottom  pad  has  two  syphons, 
the  ends  of  which  are  immersed  in  the  oil  reservoir  and  thus  lubri- 
cate the  dust  guard  and  prevent  wear. 

264 


RAILWAY  ROLLING  STOCK 


265 


Most  dust  guards  get  little  or  no  lubrication,  and  when  they 
are  worn  they  no  longer  keep  the  dust  out  as  efficiently  as  one 
might  desire. 

Between  the  top  of  the  "  brass  "and  the  cover  of  the  axle  box, 
to  which  the  weight  is  transmitted  through  the  springs,  is  placed 
a  hardened  cast  steel  liner  or  wedge  piece,  which  serves  to  dis- 
tribute the  load  uniformly  over  the  whole  of  the  brass. 

Inside  axle  boxes  consist  of  two  almost  semi-circular  castings 
with  vertical  side  plates  which  fit  the  horn  plates;  the  lower  half 
is  suspended  from  the  upper  half  by  bolts  and  the  springs  rest 
upon  the  upper  half. 

Journals  and  Bearings. — It  has  become  a  general  practice  to 
roll  the  journals  of  crank  pins  and  axle  journals  with  a  hard  steel 
roller,  in  order  to  compress  the  surface  and  make  it  very  tough, 


FIG.  98. — Axle  box  with  rain  guard. 

and  capable  of  resisting  wear.  The  roller  is  held  in  the  tool  post 
of  the  lathe  after  the  finishing  cut  has  been  taken  and  is  forced 
against  the  journal.  This  same  method  is  also  frequently  used 
for  rolling  the  white  metal  in  babbitted  bearings. 

As  regards  bearing  metals,  locomotive  driving  and  trailing 
bearings  are  usually  bronze  lined  with  white  metal,  and  the  ten- 
dency is  to  extend  the  use  of  white  metal  as  a  lining  for  bearings. 
The  reason  for  this  tendency  is  that  a  good  white  metal  combines 
the  necessary  strength  with  plasticity.  It  contains  hard  grains 
which  transmit  the  pressure  to  a  plastic  matrix.  The  hard  grains 
prevent  excessive  wear,  and  as  they  are  embedded  in  a  yielding 
matrix  the  load  is  evenly  distributed  over  the  entire  surface. 

With  phosphor  bronze,  unless  the  bearings  are  very  carefully 
scraped  together,  the  load  is  not  so  evenly  distributed,  and  in  the 
case  of  shocks  and  vibration,  local  heating  may  easily  occur, 
causing  a  hot  bearing. 


266  PRACTICE  OF  LUBRICATION 

It  is  a  well-known  fact  that  in  running  down  a  long  gradient, 
crank  pins  with  bronze  bearings  are  liable  to  heat,  due  to  excessive 
shocks  in  the  bearings  caused  by  the  absence  of  steam  in  the 
cylinders,  which  otherwise  would  "cushion"  the  blow  at  either 
end.  Strips  of  white  metal  embedded  in  the  crank  pin  bearings 
help  to  prevent  such  heating. 

Another  reason  for  the  wider  adoption  of  white  metal  is,  that 
should  the  bearing  seize,  the  shaft  is  only  little  affected,  and  the 
bearing  can  be  rebabbitted  at  a  small  cost. 

A  large  proportion  of  lead  in  white  metal  is  not  desirable,  as  it 
causes  increased  friction,  and,  being  a  bad  conductor  of  heat, 
does  not  allow  the  heat  to  be  dissipated  so  readily;  consequently 
the  bearings  run  warmer.  Furthermore,  lead  is  more  easily 
attacked  by  acids  which  may  be  present  in  the  oil. 

It  is  necessary  for  the  white  metal  to  be  supported  by  brass  or 
cast-iron  of  sufficient  thickness  to  avoid  distortion  under  running 
conditions.  If  the  brasses  are  too  light,  they  may  crack,  or  at 
least  run  exceedingly  warm.  This  action  causes  the  edges  of 
the  brass  to  pinch  the  journal  and  makes  it  very  difficult  for  the 
oil  to  do  its  work  properly. 

As  mentioned  above,  phosphor  bronze  can  be  used  as  a  bearing 
metal  only  when  the  faces  are  very  accurately  scraped  together. 
In  the  case  of  white  metals,  however,  such  careful  fitting  is  not 
necessary,  as  the  bearing  surfaces  will  bed  themselves  together 
more  readily. 

Of  recent  years  bronzes  of  a  new  type  called  "  plastic  bronzes" 
have  been  used,  particularly  in  the  United  States.  The  differ- 
ence between  them  and  the  white  metals  is  that  they  are  made 
up  of  plastic  substances  embedded  in  a  hard  matrix,  whereas 
the  white  metals  are  made  up  of  hard  substances  embedded  in  a 
soft  matrix.  There  seems  to  be  a  divergence  of  opinion  as  tq 
the  utility  of  these  plastic  bronzes. 

THE  PROPORTIONS  OF  ROLLING  STOCK  JOURNALS 

It  is  very  important  that  the  load  on  journals  shall  not  be  trans- 
mitted eccentrically.  Take  a  journal  with  a  diameter  D  and 
length  L,  the  load  being  not  in  the  centre,  but  transmitted  at  a 
point  x  inches  away  from  the  centre  (Fig.  99)  ;  then  the  bearing 
pressure  at  the  extreme  ends  of  the  bearing  will  be 


L 

To  take  an  example:  Let  P  be  16,000  Ibs.,  the  diameter  8  in., 
and  the  length  10  in.     If  the  load  be  central  the  pressure  per 


RAILWAY  ROLLING  STOCK 


267 


square  inch  will,  bo  200  Ibs.  uniformly  distributed.  If  2  in.  are 
added  to  the  inside  of  the  box,  making  the  length  12  in.  and  x 
equal  to  1  in.,  then  the  maximum  and  minimum  pressure  per 
square  inch  will  be  249  Ibs.  and  83  Ibs.  respectively  at  the  outside 
and  inside  edges,  while  the  average  pressure  is  only  166  Ibs.  per 
square  inch.  This  will  indicate  that  it  is  often  preferable  to 
accept  an  increased  pressure  per  square  inch  rather  than  create 
an  eccentric  loading. 

On  locomotive  driving  journals  the  brass  covers  half  the  jour- 
nal and  the  pressures  per  square  inch  are  usually  somewhere 
about  200  Ibs. 

In  the  case  of  car  and  tender  bearings  the  arc  over  which  the 
brass  touches  the  journal  is  usually  90  degrees,  occasionally 
120  degrees,  and  the  pressure  per  square  inch  of  projected  area  is 
usually  from  300-325  Ibs. 

The  small  space  available,  parti- 
cularly on  narrow  gage  railways,  often 
makes  it  difficult  to  give  locomotive, 
bearings  the  dimensions  required  foi 
cool  running.  The  journals  can 
always  be  made  strong  enough,  but 
the  difficulty  is  to  make  them  long 
enough.  When  a  bearing  runs  con- 
sistently hot,  an  increase  in  journal 
diameter  is  n  o  remedy,  as,  although 
the  bearing  pressure  per  square  inch 
is  reduced,  the  surface  area  and  sur- 
face speed  of  the  journal  are  both  in- 
creased, so  that  notwthstanding  the  larger  radiating  surface, 
no  advantage  is  obtained.  With  greater  length  of  the  journal, 
the  surface  area  is  increased,  but  not  the  surface  speed,  and  the 
result  is  a  cooler  running  bearing. 

Some  interesting  information  was  given  by  Mr.  T.  Robson 
in  an  article  in  "  Engineering "  for  November  25.  1910,  in 
which  he  gives  an  empirical  formula  for  judging  whether  a  bear- 
ing will  be  inclined  to  overheat  or  not. 

Let  S  =  the  maximum   continuous  speed  of  the    vehicle    in 

miles  per  hour. 

D  =  the  diameter  of  the  wheel  in  inches. 
W  =  the  weight  on  journal  in  tons. 
L  =  the  effective  length  of  the  journal  in  inches. 


Fro.  99. —  Eccentric  loading;. 


Then, 


wxs 

L 


K  being  a  constant,  which  is  determined 


X  D' 
by  actual  experience, 


268 


PRACTICE  OF  LUBRICATION 


The  article  gives  values  for  this  constant  for  different  bearings, 
all  of  which  are  white  metalled  and,  except  in  the  ease  of  crank 
pins,  lubricated  by  means  of  a  pad  or  oil  saturated  waste  below 
the  journal. 

Mr.  Robson  gives  his  experience  with  various  bearings,  inclined 
to  heat,  and  others,  which  owing  to  longer  journals,  ran  reasonably 
cool. 

A  summary  of  Mr.  Robson's  recommendations  is  given  in 
Table  No.  10. 

TABLE  No.  10 


Type  of  bearings 

Maximum 
speed  in  miles 
per  hour 

Value  for  K 

Inside  locomotive  journals  on  carrying  axles  and 
bogies 

70 

0   8 

Outside  journals  on  locomotives  and  tenders  .  .  . 
Crank  pin  journals 

70 

70 

0.9 

4  0  to  4  5 

(For  some  inside  crank  pins  K  was  5.6  which  was 
too  high,  but  could  not  be  reduced  on  account  of 
the  narrow  track) 

Carriage  journals  
Goods  and  mineral  wagon  journals  .  . 

70 
25 

0.7 
0.5 

METHODS  OF  LUBRICATION 

Locomotive  Axle  Boxes. — The  usual  practice  is  by  means  of 
syphon  oil  feeds  (tail  trimmings)  from  auxiliary  oil  boxes,  the 
oil  being  led  through  tubes  to  the  top  of  the  bearings,  entering 
the  bearing  through  either  a  central  oil  hole  into  one  longi- 
tudinal oil  channel  at  the  top  of  the  brass,  or  through  two  oil 
holes  leading  into  two  oil  grooves  forming  a  slight  angle  with  the 
journal.  By  this  system  the  oil  enters  the  bearing  only  with 
difficulty,  except  at  the  two  bearing  ends,  and  once  it  has  left 
the  bearing  the  oil  is  lost. 

In  modern  systems  the  boxes  are  fitted  with  oiling  pads 
underneath  the  journals,  or  they  are  filled  with  waste,  preferably 
woollen  waste  thoroughly  saturated  with  oil.  The  oil  that  enters 
the  bearing  is  caught  by  the  pad  or  the  waste,  and  distributed 
over  the  entire  underside  of  the  journal.  The  lower  edges  of 
the  brass  are  eased  away,  so  as  to  facilitate  the  entrance  of  the  oil 
film  between  the  journal  and  the  brass. 

The  most  recent  practice  is  to  instal  mechanically  operated 
forced-feed  lubricators  on  the  frame  or  in  the  cab,  from  which 
the  oil  is  automatically  distributed  to  the  axle  boxes  under  pres- 
sure. Test-cocks  are  provided  in  suitable  positions,  so  as  to 


RAILWAY  ROLLING  STOCK  269 

regulate  and  test  the  oil  feed.  This  method  is  an  ideal  one,  as  it 
ensures  a  feed  of  oil  to  the  bearings  in  direct  proportion  to  the 
revolutions  of  the  journal;  also  this  method  is  unquestionably 
the  most  economical,  and  the  oil  reaches  the  bearings  with  absolute 
certainty,  the  distribution  being  entirely  automatic. 

Where  mechanical  lubricators  are  used  for  feeding  oil  both 
to  the  cylinders  and  to  the  axle  boxes,  such  lubricators  should 
have  two  compartments,  so  that  a  bearing  oil  may  be  used  for 
the  axles,  and  cylinder  oil  for  the  cylinders.  Obviously,  it  is 
ordinarily  not  desirable  to  use  cylinder  oil  for  the  axle  boxes,  as 
it  is  far  too  viscous  and  causes  unnecessarily  high  temperatures 
of  the  journals  and  boxes. 

In  the  case  of  bogey  boxes,  oiled  through  syphons  from  the  top, 
they  are  exposed  to  rain,  or  to  the  spray  of  water  from  the  cylinder 
waste-water  cocks.  If  sufficient  water  enters  the  oil  well  on  top 
of  the  box,  it  will  dislodge  the  oil,  and  thus  cause  a  heated  journal. 
There  is  a  general  tendency  among  engine  drivers  to  fill  up  the 
oil  wells  too  high,  and  during  running  the  vibration  and  oscilla- 
tion causes  the  oil  to  splash  over  the  edge  of  the  box,  causing 
unnecessary  waste.  To  overcome  this  the  best  method  is  to 
fill  the  oil  well  with  saturated  waste,  interlacing  the  oil  syphons 
into  same,  and  oil  can  then  be  added  to  the  waste  as  required. 
This  will  prevent  the  entrance  of  water,  and  will  also  prevent 
waste  of  oil. 

Axle  Boxes  for  Tenders  and  Cars. — In  many  cases  pads 
are  used  for  the  underside  of  the  journal,  plus  an  additional  oil 
feed  by  means  of  syphons  arranged  in  the  top  of  the  boxes.  The 
best  practice  is  to  use  a  pad  or  waste  in  the  boxes,  and  rely  on 
these  for  the  lubrication  without  any  additional  oiling  from 
above ;  this  permits  doing  away  entirely  with  oil  grooves  in  the 
bearings,  so  that  the  whole  bearing  surface  is  available  to  carry 
the  load. 

Pad  Oilers. — The  best  known  make  of  these  oilers  is  the  Arm- 
strong oiler,  Figs.  97  and  100,  which  has  given  general  satisfaction 
and  is  extensively  used.  The  Armstrong  oiler  consists  of  a  pad  on 
a  light  frame,  supported  by  resilient  steel  springs.  The  pad  is 
so  woven  that  the  points  of  the  pile  only  lightly  touch  the  journal. 
This  pile  is  made  of  a  special  mixture  of  cotton  and  wool  in  order 
to  retain  the  oil  drawn  up  from  the  well  of  the  box  by  the  feeders, 
which  should  have  high  capillary  powers.  The  buttons,  which 
are  made  of  lignum  vitae,  act  as  buffers  jind  prevent  the  pile  of 
the  pad  from  being  flattened  out  and  glazed;  in  this  way  the 
capacity  of  the  pad  for  supplying  oil  to  the  face  of  the  journal 
remains  unimpaired  for  a  long  period.  New  oilers  should  be 


270 


PRACTICE  OF  LUBRICATION 


dried  and  soaked  in  oil  for  about  twelve  hours  before  being  placed 
in  the  axle  boxes.  About  one  pint  of  oil  should  be  supplied  to 
each  axle  box,  or  sufficient  to  cover  the  bottom  of  the  well  to  the 
depth  of  J^  inch,  and  a  similar  quantity  about  every  3,000  miles. 
If  the  axle  boxes  are  dust-proof  and  the  oilers  are  kept  free  from 
grit  and  properly  fitted,  the  makers  claim  that  they  will  last 
250,000  miles  without  repair  or  removal,  and  guarantee  that  they 
will  last  for  100,000  miles. 

Pad  oilers  like  the  Armstrong  oiler  will  lubricate  the  journal 
however  high  the  journal  speed  may  be,  and  the  action  is  un- 
affected by  frequent  changes  in  the  direction  of  rotation. 

The  use  of  such  oilers  results  in: 

Ample  and  uniform  oil  distribution. 


FIG.  100.— Pad  oilers. 

Freedom  from  "hot  boxes"  under  most  conditions. 

Less  necessity  for  frequent  periodical  inspection  of  axle  boxes. 

Reduction  in  oil  consumption  and  other  general  lubricating 
charges. 

Waste  Oiling. — rGood  wool  waste  should  be  soaked  with  the 
proper  seasonable  kind  of  oil  for  at  least  48  hours  before  being  used. 
The  surplus  oil  should  be  drained  off,  allowing  sufficient  oil  in  the 
waste  so  that  it  will  show  under  slight  pressure.  If  there  is  too 
much  oil  in  the  waste,  the  waste  becomes  too  heavy,  and  will  fall 
away  from  the  journal,  thus  depriving  the  bearing  of  lubrication 
altogether.  Well  soaked  waste  will  have  absorbed  approximately 
five  times  its  own  weight  of  oil. 

The  first  waste  (Fig.  10M)  should  be  moderately  dry  and 
packed  tightly  around  the  back  end  of  the  box,  so  as  to  make 
a  guard  for  the  purpose,  not  only  of  retaining  the  oil,  but  of  ex- 


RAILWAY  ROLLING  STOCK 


271 


chiding  the  dust.  Then  the  box  should  be  packed  with  the 
drained  waste,  made  into  balls,  firmly  enough  so  that  it  will  not 
fall  away  from  the  journal  when  the  car  runs  over  crossings,  etc., 
but  not  so  tightly  as  to  squeeze  out  the  oil.  The  waste  should  be 
kept  even  with  the  journal,  an  inch  below  the  edges  of  the  brass. 
This  is  most  important,  as  waste  packed  too  high  will  be  caught 
and  carried  round,  causing  a  hot  box. 

.  At  high  journal  speeds,  say  above  300  ft.  per  minute,  the  waste 
is  inclined  to  be  pushed  over  to  one  side  of  the  box  by  the  friction 
between  the  journal  and  the  waste,  and  there  compressed  so  tightly 
that  lubrication  becomes  deficient.  There  is  one  type  of  box 
which  has  three  compartments  divided  by  longitudinal  ribs, 
thus  effectively  preventing  the  waste  from  moving  and  ensuring 
uniform  saturation  of  the  waste  all  through. 


ection 


FIG.   101.  —  Waste  oiling. 


The  waste  in  the  front  end  of  the  box  should  be  as  high  as  the 
opening,  and  have  no  thread  connection  with  the  waste  under- 
neath the  journal.  This  waste  should  be  placed  in  the  box  by 
hand  after  the  box  has  been  packed.  It  performs  no  service 
other  than  to  act  as  a  stopper  to  prevent  the  waste  that  is  doing 
the  work  of  lubrication  from  working  forward. 

It  is  important  to  give  some  intelligent  attention  to  the  waste  in 
the  boxes  during  service,  the  chief  requirement  apart  from  oiling 
being  to  lightly  loosen  the  waste  packing  on  either  side  of  the  j  ournal 
for  about  every  1000  miles'  run,  to  bring  it  into  good  contact 
with  the  j  ournal  and  avoid  the  hardened  and  glazed  condition  which 
is  gradually  brought  about  by  contact  with  the  revolving  journal. 
Suitable  tools  for  this  purpose  and  also  for  packing  the  boxes  are 
shown  in  Figs.  102  A,  B,  and  C  showing  a  packing  knife,  hook, 
and  loosening  tool  respectively.1 

Dust  Guards. — Efficient  dust  guards  to  prevent  the  entrance 
of  dust  are  of  the  very  greatest  importance.  Too  much  attention 

1  Copied  from  American  Locomotive  Dictionary. 


272 


PRACTICE  OF  LUBRICATION 


cannot  be  paid  to  this  matter,  as,  if  dust  and  grit  are  allowed  to 
enter,  the  lubrication  can  never  be  perfect,  and  pad  oilers  and 
waste  are  liable  to  be  choked.  The  dust  trouble  is  particularly 
prominent  in  countries  like  the  South  of  England,  due  to  the 
lime  dust. 

In  the  case  of  newly-laid  roads,  it  frequently  happens  that  fine 
granite  dust  causes  trouble,  being  very  hard  and  very  fine  it 
enters  the  boxes,  and  may  cause  a  great  deal  of  wear. 

Inspection  and  Oiling  of  Axle  Boxes. — Although  as  a  general 
rule  it  is  true  that  regular  and  careful  inspection  of  axle  boxes  is 


A  :^      Steel  Handle 


Steel 
Hook  to  Open  und  Haudle 

Box    Lids 
.24 


FIG.  102. — Packing  tools. 

desirable,  yet  it  is  also  true  that  there  can  be  too  much  inspection. 
As  a  matter  of  fact,  pad  oilers  (and  this  also  refers  to  woollen 
waste),  once  they  are  well  fitted  and  work  well,  should  not  be 
disturbed  in  any  way.  An  examination  every  three  months  will, 
as  a  rule,  be  quite  sufficient,  and  at  the  same  time  a  small  quan- 
tity of  oil  may  be  introduced  in  the  box,  assuming  that  there  is  no 
additional  oil  supply  from  the  top. 

The  oil  consumption  with  waste  packing  ranges  from  500  miles 
to  4,000  mites  per  pint  of  oil,  a  good  average  being  3,000  miles 
per  pint  of  car  oil. 


RAILWAY  ROLLING  STOCK  273 

Special  Oiling  Systems. — Lubrication  of  axle  boxes  by  means 
of  a  circulation  system  has  attracted  considerable  attention. 
Several  systems  have  been  tried,  including  a  force-feed  circula- 
tion system  by  means  of  a  rotary  oil  pump,  and  also  a  system  con- 
sisting of  a  round  disc  fixed  to  the  front  end  of  the  journal, 
dipping  in  the  oil  in  the  bottom  of  the  box,  and  lifting  the  oil  to 
the  top  of  the  box,  from  which  it  flows  into  the  bearing  in 
liberal  quantities. 

It  is  obviously  desirable  (particularly  in  railway  practice)  to 
give  the  journals  as  liberal  a  supply  of  oil  as  possible.  The 
difficulties  are,  that  it  is  not  easy  to  prevent  excessive  leakage  of 
oil  through  the  ends  of  the  box;  and  that  the  entrance  of  dust  and 
dirt  makes  the  oil  dirty,  and  may  cause  clogging  of  oil  pipes  where 
such  exist.  Other  mechanical  appliances  have  been  tried,  such 
as  rollers  against  the  under  side  of  the  journals,  but  have  not  been 
successful. 

It  must  be  kept  in  mind  that  whatever  appliance  is  used,  it 
should  be  so  designed  that  it  is  not  liable  to  get  out  of  order;  for 
instance,  the  clogging  of  an  oil  pipe,  or  the  breakage  of  an  oil 
pipe  due  to  vibration,  will  cause  stoppage  of  the  oil  supply  al- 
together, with  disastrous  results. 

Connecting  Rods  and  other  Parts. — The  brasses  in  connecting 
rod  bearings  must  be  let  completely  together  so  as  to  cover  the 
entire  surface  of  the  journals  and  minimize  the  entrance  of  dust 
and  grit. 

Syphon  lubrication  is  extensively  used.  For  those  parts  which 
require  only  a  small  amount  of  oil,  trimming-pins,  or  trimming- 
plates  are  used,  being  a  piece  of  >£-in.  wire  or  Me-i*1-  plate,  which 
has  a  hole  at  the  bottom  and  also  at  the  top,  through  which  are 
threaded  one  or  two  strands  of  wool,  just  sufficient  for  proper 
lubrication  of  the  motion  bars  or  other  parts,  where  such  a  small 
amount  of  oil  is  found  ample. 

It  is  safer  to  use  syphons  than  to  feed  the  oil  through  oil  cups 
where  the  oil  feed  is  adjusted  by  means  of  a  needle  valve,  as  a 
needle  valve  is  more  easily  choked  than  a  syphon.  Figs.  103, 
104  and  105  show  various  designs  of  such  oilers. 

For  reciprocating  parts,  such  as  connecting  rod  ends,  choke  or 
plug  trimmings  are  frequently  used;  see  Fig.  106.  This  trimming  is 
pushed  well  into  the  syphon  tube,  and  prevented  from  dropping 
right  into  the  tube  by  a  big  loop,  which  rests  on  the  top  of  the 
syphon  tube.  When  the  engine  is  running,  the  oil  is  thrown  up 
into  the  syphon  tube,  and  the  trimming  being,  say,  K6  in-  below  the 
top,  a  well  or  reservoir  of  oil  is  always  maintained,  the  oil 
soaking  through  the  plug  trimming  and  entering  the  bearing. 

18 


274 


PRACTICE  OF  LUBRICATION 


The  plug  trimming  should  preferably  end  close  to  the  journal,  as 
this  largely  prevents  the  oil  being  wasted  by  escaping  between  the 
brass  and  the  strap.  Sometimes  a  little  tube  is  screwed  in  here, 
so  as  to  positively  prevent  escape  of  oil.  Plug  trimmings  may  be 


FIG.  103. 


FIG.  104. 
Locomotive  stationary  oilers. 


FIG.  105. 


made  of  copper  trimming  wire,  the  wire  being  wound  in  the  same 
manner  as  the  yarn  in  the  usual  plug  trimming.  The  advantage 
is  said  to  be  that  a  much  heavier  oil  can  be  used  than  could  pos- 
sibly syphon  through  the  ordinary  worsted  trimming.  Sometimes 


FIG.   106. — Plug  (choke)  trimming. 


FIG.   107. — Rod  needle  oiler. 


(in  Continental  practice)  oil  is  allowed  to  go  direct  into  the 
syphon  tube  through  holes  at  the  bottom;  this,  of  course,  means 
waste  of  oil  while  the  engine  is  standing.  In  America  and  on  the 
Continent,  plug  trimmings  are  frequently  discarded  in  favor 


RAILWAY  ROLLING  STOCK  275 

small  needle  valves,  consisting  of  a  loose  fitting  pin  with  a  head  at 
the  top,  Fig.  107,  the  upward  and  downward  motion  of  the  pin 
being  regulated  by  an  adjustable  stop  in  the  oil  cup  cover. 

Another  method  is  to  have  simply  a  long  thin  piece  of  wire  bent 
over  at  the  top,  fitted  in  the  syphon  tube,  passing  through  a  small 
fitting  screwed  into  the  top  of  the  syphon  tube,  and  having  a  cen- 
tral opening  through  which  the  wire  or  needle  passes  down.  The 
difference  in  diameter  between  the  needle  and  the  opening  deter- 
mines the  oil  feed. 

In  oil  cups  that  are  entirely  enclosed,  the  cover  should  have  a 
tiny  hole  to  allow  the  air  to  get  in  as  the  oil  leaves  the  cup,  or 
the  hole  in  the  cover  should  be  plugged  up  with  a  piece  of  cane 
(which  is  porous),  or  a  piece  of  cork  with  a  V-groove  at  the  side. 

When  changing  over  from  an  oil  largely  vegetable  or  animal 
in  character,  it  nearly  always  happens  that  the  syphons  and  trim- 
mings get  more  or  less  choked  with  deposit  due  to  the  change. 
It  is  therefore  to  be  recommended,  wherever  any  drastic  change 
in  oils  is  to  be  carried  out,  that  new  trimmings  be  made  for  all 
the  oil  cups  and  lubricators. 

The  consumption  of  engine  oil  for  the  various  external  parts  of 
a  locomotive,  including  axle  boxes,  varies  considerably  according 
to  the  size  and  the  method  of  lubrication.  The  consumption 
may  be  as  low  as  2  pints  per  100  miles  and  as  high  as  8  pints  per 
100  miles,  the  average  being  about  3J^  pints  per  100  miles. 

When  sharp  curves  are  frequent  it  is  desirable  to  oil  the  wheel 
flanges  by  means  of  a  jet  of  oily  steam.  Various  forms  of  lubri- 
cators are  employed  for  this  purpose;  they  all  endeavor  to 
atomize  the  oil  with  a  jet  of  steam,  which  is  then  directed  on 
to  the  wheel  flange. 

Methodical  Oiling. — It  is  very  important  that  the  oiling  of  the 
locomotive  be  carried  out  in  a  methodical  manner,  the  oiler  go- 
ing round  from  one  part  of  the  engine  to  another,  oiling  always 
in:  the  same  manner  of  rotation.  This  is  the  only  way  in  which 
he  can  be  reasonably  sure  of  not  forgetting  some  of  the  parts 
As  a  matter  of  fact,  lack  of  attention  to  this  point  may  be 
said  to  be  very  largely  responsible  for  bearing  troubles.  This 
also  applies  to  the  attention  that  should  always  be  given  to 
taking  out  syphons  or  trimmings  wherever  possible  when  the 
locomotive  has  finished  the  journey.  Overfilling  of  oil  holes  or 
oil  cups  should  be  avoided  as  it  is  wasteful  and  -does  not  im- 
prove lubrication. 

GREASE  LUBRICATION   FOR   LOCOMOTIVES   AND    CARS 

In  the  United  States  the  use  of  grease  on  locomotives  has  dur- 
ing recent  years  been  given  some  considerable  attention,  not 


276 


PRACTICE  OF  LUBRICATION 


only  for  the  connecting  rods  and  coupling  rods,  but  also  for  the 
axle  boxes. 

Fig.  108  shows  the  grease  cup  arrangement  for  one  of  the  rods; 
when  the  lock  nut  (l)is  loosened  the  threaded  plug  (2)  can  be  given 


FIG.  108. — Rod  grease  cup. 

a  turn  and  again  locked;  the  grease  gets  squeezed  into  the  bearing 
and  is  gradually  consumed,  until  the  plug  is  given  another  turn, 
and  so  on. 

Fig.  109  shows  the  application  of  grease 
to  a  driving  box;  the  grease  is  moulded  to 
the  shape  of  the  cellar  and  placed  on  the 
follower  plate  (1) ;  the  spring  (2)  pushes  the 
follower  plate  upward,  thus  squeezing  the 
grease  through  the  perforated  plate  (3) 
shaped  to  the  contour  of  the  journal  and 
3  kept  at  a  distance  of  about  Y%  inch. 

Oil  grooves  are  cut  to  distribute  the 
grease  as  shown;  the  vertical  grooves  are 
cut  only  on  the  "off  side"  of  the  brass, 
presumably  to  act  as  drainage  grooves. 
Through  a  hole  shown  on  the  left  some 
grease  reaches  the  hub  face  of  the  wheel ; 
not  shown,  is  arranged  for  lubricating  the 


FIG.    109. — Driving  box 
grease  lubrication. 


a   similar   hole, 
hornplates. 


RAILWAY  ROLLING  STOCK  277 

It  is  stilted  l).v  the  m.'ikers  of  those  grease  appliances  that  the 
grease  recommended  for  (lie  tixle  boxes  must  not  get  sticky  when 
worked  between  the  fingers,  and  when  smeared  with  a  penknife 
on  a  piece  of  white  paper  small  bubbles  of  water  must  appear  on 
the  surface.  The  author  has  no  personal  experience  with  these 
greases;  they  are  probably  rather  soft  low  melting  point  greases 
somewhat  similar  to  the  English  railway  wagon  greases  men- 
tioned below,  and  containing  a  certain  amount  of  water,  to  bring 
about  emulsification,  so  that  the  journal  when  revolving  may 
continue  to  abrade  or  melt  the  grease. 

It  is  obvious  that  whatever  claims  may  be  substantiated  in 
the  way  of  " economy"  and  ability  to  stand  up  to  severe  condi- 
tions, the  amount  of  power  lost  in  friction  is  considerably  in- 
creased with  grease  lubrication,  and  also  the  wear. 

An  advantage  with  grease  lubrication  is  that  the  starting  fric- 
tion is  lower  than  with  oil  on  account  of  the  thicker  film  between 
the  surfaces. 

Some  tests  were  carried  out  in  1904  at  the  St.  Louis  Exhibition 
on  locomotives,  using  grease  and  oil.  A  consolidated  type  loco- 
motive, 22"  X  28",  8-wheel  coupled,  2  wheels  in  front  (2-8), 
developing  a  maximum  power  of  1,000-1,100  H.P.  showed  a  f no- 
tional loss  as  follows: 

Oil:  at  15  miles  per  hr.  :  61  H.P. 
at  30  miles  per  hr.  :  107  H.P. 

Grease  :a,t  26.6.  miles  per  hr.  :224  H.P. 

A  Pennsylvania  consolidated  type  locomotive,  developing  a 
maximum  power  of  1,000-1,100  H.P.  consumed  in  friction  alone 
when  using  grease  throughout : 

With  Grease: at  15  miles  per  hr.  :  132  H.P. 
at  30  miles  per  hr.  :  224  H.P. 

It  was  demonstrated  that  wear  of  axles  and  crank  pins  was 
greater  with  grease  than  with  oil,  and  that  there  was  not  much 
difference  in  the  cost  of  lubrication,  the  consumption  with  grease 
being  approximately  450  miles  per  pound  of  lubricant. 

Outside  the  United  States  grease  has  not  been  favored  for 
locomotive  lubrication;  in  Europe  oil  is  used  everywhere  in  pref- 
erence to  grease. 

In  Great  Britain  grease  is,  however,  still  used  for  lubricating 
colliery  trucks  and  goods  wagons,  but  this  practice  is  rapidly 
dying  out  in  favor  of  oil. 

The  grease  is  placed  in  a  cavity  formed  in  the  top  of  the  axle 
box.  Large  openings  in  the  bottom  of  this  cavity  communicate 
with  similar  openings  in  the  brass,  and  under  the  influence  of 
frictional  heat  the  grease  gradually  melts  and  lubricates.  The 


278  PRACTICE  OF  LUBRICATION 

friction  is  high;  the  boxes  are  often  neglected,  lids  are  torn  off, 
and  the  grease  cavities  contaminated  with  dirt,  water,  etc.  Al- 
together the  results  are  such  that  the  sooner  this  form  of  lubrica- 
tion is  done  away  with  in  favor  of  oil  lubrication  the  better. 

On  page  27  will  be  found  some  information  about  the  manu- 
facture and  constituents  of  such  railway  wagon  greases. 

Railway  Oils. — The  character  of  railway  oils  is  governed  to  a 
large  extent  by  the  climatic  conditions.  In  the  Tropics  the  oil 
is  exposed  to  very  high  temperatures  during  the  day  and  quite 
low  temperatures  during  the  night.  Long  distance  trains  going 
from  a  warm  low-lying  country  into  a  cold  mountainous  district 
will  find  themselves  exposed  to  widely  varying  temperature  con- 
ditions during  their  journey.  In  temperate  climates  the  same 
conditions  exist  except  that  the  differences  between  the  day  and 
night  temperatures  are  smaller;  still  the  variation  in  temperature 
may  be  quite  considerable.  For  example,  the  Scottish  express 
trains  running  between  London  and  Scotland  will  meet  tempera- 
tures in  the  North  very  appreciably  lower  than  the  temperatures 
in  the  South. 

These  conditions  call  f or '.  oils  with  low  setting  points  in  order 
that  they  may  feed  as  uniformly  as  possible  and  with  certainty 
through  the  oil  syphons  and  other  feeding  appliances. 

On  the  other  hand,  once  the  oil  has  entered  the  bearing  sur- 
faces it  is  exposed  to  considerable  pressure  and  high  temperature, 
so  that  it  must  possess  great  oiliness  at  the  bearing  temperature. 
In  brief,  railway  oils  must  have  viscosities  which  are  not  unduly 
influenced  by  great  variations  in  temperature.  The  oils  which 
best  satisfy  these  requirements  are  mixtures  of  non-paraffinic 
base  mineral  oils  with  setting  points  in  the  neighborhood  of 
zero  °F.  mixed  with  from  10  per  cent,  to  25  per  cent,  or  even 
more  of  a  suitable  fixed  oil.  Mineral  oil  of  the  character  de- 
scribed will  give  fluidity  in  the  cold,  and  the  admixture  of  fixed 
oil  has  the  effect  of  maintaining  great  oiliness  and  viscosity  at 
high  temperatures. 

The  admixture  of  fixed  oil  serves  another  purpose  in  the  case 
of  locomotive  engine  oil,  in  that  it  prevents  the  oil  from  being 
washed  away  from  the  bearing  surfaces  by  the  steam  which 
escapes  from  the  piston  rod  and  valve  rod  gland,  the  condensed 
steam  producing  a  "lather"  on  the  guides  and  other  parts. 

The  setting  points  required  for  the  blended  oil  can  be  deter- 
mined only  on  the  road,  although  syphoning  tests  may  be  carried 
out  in  the  Laboratory  indicating  the  syphoning  and  the  capillary 
power  of  the  oil  at  different  temperatures,  including  the  lowest 
temperatures  to  which  the  oil  will  be  exposed  during  service. 


RAILWAY  ROLLING  STOCK  279 

Such  syphoning  tests  are  not  much  used  by  railways,  and  yet 
they  are  of  the  very  greatest  importance. 

Oils  differ  very  considerably  in  their  ability  to  syphon,  and 
furthermore,  the  quality  of  wool  on  the  market  varies  very 
considerably  in  its  syphoning  qualities.  In  the  case  of  syphon 
oilers,  the  wool  which  will  give  the  greatest  syphoning  effect  for 
the  class  ol  oil  in  use  is  the  most  desirable  to  use.  In  the  case 
of  pad  oilers,  which  are  fixed  below  the  axles  and  lift  the  oil  from 
the  bottom  of  the  box,  the  ability  of  the  pad  and  its  feeders  to 
draw  the  oil  and  hold  it  is  most  important.  It  will  be  found  that 
the  quality  of  wool  required  for  the  two  purposes  is  different. 
Wool  or  cotton  which  will  lift  the  oil  a  considerable  distance  and 
hold  it  there  will  not  easily  deliver  the  oil  to  the  journal,  nor 
will  it  have  good  syphoning  qualities  when  used  in  a  syphon  oil 
cup. 

As  regards  the  viscosity  of  railway  oils,  it  is  always  desirable 
that  the  viscosity  should  alter  as  little  as  possible  per  degree 
Fahrenheit.  As  a  rule,  the  more  fluid  the  oil,  the  quicker  will  it 
feed  through  the  lubricating  appliances,  and  consequently  if  the 
oil  varies  greatly  in  viscosity  with  a  varying  temperature,  the 
feed  will  be  irregular  and  wasteful.  When  comparing  oils  for 
change  in  viscosity  due  to  increase  in  temperature,  the  oils  least 
affected  at  the  bearing  temperatures  are  the  free-flowing  vegetable 
or  animal  oils,  while  mineral  lubricating  oils  made  from  either 
paraffin  base  crudes  or  asphaltic  crudes  are  distinctly  inferior 
in  this  respect.  When  the  running  temperatures  are  low,  ap- 
proaching freezing  point,  the  comparison  may  fall  out  differently 
as  most  vegetable  and  animal  oils  (as  well  as  paraffin  base  lubri- 
cating oils)  have  a  poor  cold  test,  whereas  asphaltic  base  oils 
still  flow  freely. 

The  selection  of  the  right  quality  of  vegetable  or  animal  oil  is 
very  important,  because  unsuitable  fixed  oils  usually  become  acid 
during  use,  and  have  a  strong  tendency  to  oxidize  and  produce 
gummy  deposits.  The  acidity  has  an  effect  on  the  bearing 
metal,  and  that,  in  connection  with  the  gumminess  produced 
by  the  oil,  attracts  and  fixes  the  dust  and  dirt  which  enter  the 
bearing.  As  a  result,  the  oiling  pads  or  oiling  waste,  or  the  oil 
syphons,  become  choked  and  more  or  less  inoperative,  due  to 
the  deposit. 

The  fixed  oils  used  for  compounding  locomotive  engine  oils 
may  be  rape  oil,  olive  oil,  or  whale  oil,  or  mixtures  of  these;  rape 
oil  and  whale  oil  are  usually  used  in  the  form  of  blown  oils,  blown 
to*a  viscosity  of  400"  to  720"  Saybolt  at  212°F.  and  the  per- 
centage ranges  from  10  per  cent,  to  25  per  cent.,  the  same  as 


280 


PRACTICE  OF  LUBRICATION 


for  marine  engine  oils;  in  fact  the  character  of  the  oils  is  very 
similar. 

Car  oils  are  usually  dark  lubricating  oils,  containing  less 
than  3  per  cent,  of  asphaltic  matter,  and  preferably  compounded, 
although  not  to  the  same  extent  as  locomotive  engine  oils,  as  the 
bearing  pressures  which  they  have  to  withstand  are  much  less. 

Car  oils  are  preferably  compounded  with  8  per  cent,  to  12 
per  cent,  of  animal  oil  (blown  vegetable  oils  are  apt  to  clog  the 
pads).  They  are  often  used  straight,  i.e.,  not  compounded,  on 
account  of  the  lower  price  per  gallon. 

The  following  specifications  are  typical  of  locomotive  engine 
oils  and  car  oils: 

TABLE  No.   1 1 


Specific 
gravity 


Savbolt  viscosity 
at 


Per 

cent.        Set- 
of  ting          Color 


104°F. 

140°F. 

212°F. 

com- 
pound 

point, 
°F. 

i                  1 
Locomotive  engine  oil,  sum- 

' 

mer  grade                                    0  920        500 

195 

66 

15-25 

10 

Dark  rod 

Locomotive  engine  oil,  win- 

ter grade  0.920        360 

155 

56 

10-20 

0 

Dark  red 

Car  oil,  summer  grade  0  .  930        600 

235 

65 

8-12 

10 

Black 

Car  oil,  winter  grade  0.930        500 

190 

60 

5-10 

0 

Black 

In  exceptionally  cold  climates  lower  setting  points  may  be 
required,  and  when  locomotive  bearings  are  abnormally  loaded, 
a  greater  percentage  of  compound  than  recommended  above 
may  be  needed,  even  to  the  extent  of  using  pure  rape  oil  or  pure 
castor  oil.  Pure  castor  has  here  the  advantage  over  other  fixed 
oils  of  possessing  an  excellent  cold  test,  which  under  great  varia- 
tions in  temperature  is  of  great  value. 


CHAPTER  XIX 
ELECTRIC  STREET  AND  RAIL  CARS 

Street  cars  are  nearly  always  driven  by  electric  motors,  but 
are  occasionally  operated  by  cables,  travelling  below  the  streets, 
as  for  example,  the  cable  trams  in  Edinburgh. 

The  important  parts  requiring  lubrication  are  the  axles,  the 
motor  and  the  gearing. 

Axle  Boxes. — The  construction  and  lubrication  are  often  very 
similar  to  railway  practice.  One  meets  all  sorts  of  combinations 
of  syphon  oiling  (from  the  top),  pad  oilers  or  oily  waste  packing 
(from  below),  the  development  being  distinctly  in  favor  of  the 
latter  oiling  methods. 

The  Armstrong  and  other  pad  oilers  are  widely  used,  but 
unfortunately  many  oil  wells  are  made  too  small,  so  that  it  is 
difficult  to  fit  the  pads,  and  the  wells  contain  too  little  oil. 

A  very  unsatisfactory  combination  ot  grease  and  oil  lubrica- 
tion is  not  infrequently  used.  The  oil  is  fed  from  below,  and  the 
grease,  filling  a  cavity  in  the  brass,  acts  as  reserve  lubricant. 
The  trouble  is  that  the  grease  becomes  softened  by  the  oil  film 
on  the  journal  and  in  time  gets  worked  into  the  pad  oiler  below 
the  axle,  choking  the  pad  and  making  it  inoperative. 

With  grease  alone,  the  friction  and  wear  are  much  greater 
than  with  oil,  and  the  necessary  period  of  oiling  and  inspection 
of  the  cars  varies  from  once  a  day  to  twice  per  week,  whereas 
with  oil  an  inpsection  once  every  two  to  six  weeks  represents 
current  practice. 

The  axle  boxes  a're  usually  fitted  with  dust-guards.  This  is 
important,  to  keep  not  only  the  dust  out,  but  also  water,  as,  on 
rainy  days  and  when  the  tracks  are  not  properly  drained,  the 
wheels  throw  the  water  about,  and  if  it  gets  inside  the  bearings 
in  any  quantity  trouble  is  sure  to  follow. 

Motor  Bearings. —  Ring  oiling  is  not  uncommonly  employed, 
and  when  suitable  shapes  of  rings  are  employed  (see  ring  oiling 
bearings  page  160)  the  rings  will  run  at  such  a  speed  that  no  oil 
spray  is  formed,  and  yet  sufficient  oil  but  not  too  much  will  be 
conveyed  to  the  journal. 

Much  trouble  has,  however,  been  experienced  with  ring  oiling 
on  electric  cars,  the  oil  escaping  from  the  bearings  and  getting  on 
to  the  commutator  and  rotor. 

281 


282 


PRACTICE  OF  LUBRICATION 


Pad  oilers  are  gaining  in  favor  both  for  motor  bearings  and 
suspension  bearings,  as  they  are  very  reliable  in  feeding  the  oil 
and  do  not  overlubricate  the  journal.  The  pad  must  be  placed 
so  that  it  rests  on  the  journal  in  a  position  where  the  oil  can  easily 
wedge  its  way  in  between  the  bearing  surfaces  (Fig.  110).  From 
the  pad  a  number  of  woollen  syphon  strands  reach  down  into  the 
oil  well,  which  may  hold  a  large  amount  of  oil,  or  if  it  is  only  small, 
the  oil  should  be  fed  continuously  to  the  well  from  an  oil  cup 
placed  in  a  suitable  position. 

Oil-soaked  waste  is  also  used  to  some  extent,  feeding  through  an 
opening  in  the  side  of  the  brass,  as  shown  in  Fig.  111.  The  open- 
ing may  be  rectangular,  with  all  sides  well  chamfered  on  the  in- 
side where  the  oil  is  to  enter  the  bearing,  and  from  each  corner  a 


FIG.   110. — Pad  oiler. 


FIG.  111. — Waste  oiling. 


shallow  oil  groove  has  been  found  advantageous  to  distribute 
the  oil,  on  account  of  the  rather  sparing  oil  supply. 

Oil  is  added  at  intervals  to  the  oil-soaked  waste  in  the  way  in- 
dicated; in  one  case  one  pint  of  oil  had  to  be  added  every  120  to 
160  miles  for  a  5)4  X  10  inch  journal  running  1,100-1,600 
R.  P.  M.,  the  weight  of  the  rotor  being  2  tons. 

An  interesting  method  of  circulation  oiling  has  been  used  for 
the  motor  bearings  on  a  South  of  England  electric  railway,  as 
shown  in  Fig.  112.  The  oil  pump  (1)  pumps  the  oil  in  the  same 
direction  independent  of  the  direction  of  its  rotation,  as  will  be 
seen  from  the  detail  drawing,  Fig.  113.  The  oil  is  forced  to  the 
diaphragm  plate  (2)  which  has  one,  two  or  three  one-mm.  holes, 
through  which  a  small  amount  of  oil  is  constantly  delivered  to 
the  bearing,  the  greater  portion  continuing  its  way  to  the  suc- 
tion joint  box  (3),  where  it  joins  the  return  oil  from  the  bearing 


ELECTRIC  STREET  AND  RAIL  CARS 


283 


and  finally  re-enters  the  oil  pump.     Each  motor  bearing  has  its 
own  independent  pump  supply,  delivery  and  return  pipes. 


FIG.    112. — Diaphragm-circulation  oiling. 


FIG.   113. — Reversible  rotary  pump. 


The  wear  of  motor  armature  bearings  on  British  street  cars 
ranges  from  5,000  to  50,000  miles  per  ^6  inch  vertical  wear,  the 


284  PRACTICE  OF  LUBRICATION 

wear  of  the  suspension  bearings  being  rather  less;  the  average 
life  of  motor  bearings  appears  to  be  10,000  to  12,000  miles. 

The  reason  for  such  large  wear  as  compared  with  stationary 
motors  is  the  effect  of  fine  hard  grit  and  dust  (wear  from  pave- 
ment, etc.)  which  are  whirled  up  by  the  wheels  and  enter  the 
bearings. 

Gear  Wheels. — Most  gear  wheels  are  enclosed  in  a  casing  and 
use  some  kind  of  a  thin  gear  grease.  The  results  are  always  inferior 
to  those  obtained  with  gear  oil,  but  of  course  the  gear  case,  if  oil 
is  to  be  used,  must  be  as  oil  tight  as  possible. 

With  grease  or  grease  and  oil  the  life  of  the  gear  wheels  may  be 
from  50,000  to  200,000,  whereas  with  oil  the  gears  last  consider- 
ably longer. 

The  pinion  wheels  do  not  last  as  long  as  the  gear  wheels,  but 
also  here  the  use  of  oil  is  conducive  to  longer  life. 

Oils. — The  oils  used  for  lubricating  the  axle  boxes  of  electric 
street  and  railway  cars  are  usually  lower  in  viscosity  than  the 
oils  used  in  railway  practice,  because  the  bearing  pressures  and 
conditions  generally  are  not  nearly  so  severe.  Bearing  oils  Nos. 
3  and  4  represent  oils  which  may  be  recommended  for  electric 
street  cars,  and  bearing  oils  Nos.  4  and  5  are  recommended  for 
electric  railway  cars.  All  of  these  oils  should  preferably  be 
compounded  with  not  more  than  10  per  cent,  of  a  non-gumming 
animal  oil  and  in  cold  climates  a  low  setting  point  would  be 
required. 

The  oils  for  motor  and  suspension  bearings  should  be  of  a 
rather  higher  viscosity  as  they  are  exposed  to  high  temperatures 
(commutator  heat)  or  pressure  (from  pinion  wheel). 

Bearings  oils  Nos.  5  or  6  may  be  recommended  and  may  with 
advantage  be  compounded  when  the  conditions  are  severe. 

As  to  gear  lubricants,  the  same  oils  as  are  used  for  the  motor 
and  suspension  bearings  can  be  used  when  the  gear  case  is  rea- 
sonably oil  tight.  When  a  more  viscous  lubricant  is  required, 
mixtures  of  oil  and  gear  grease  in  suitable  proportions,  so  that 
the  mixture  is  not  unnecessarily  heavy,  will  form  the  best 
solution. 

Wheel  Flange  Lubrication. — For  electric  locomotives  which 
have  to  negotiate  many  curves,  as  for  example  the  electric  loco- 
motive service  through  the  St.  Clair  Tunnel,  wheel  flange  lubri- 
cators have  given  excellent  service.  The  oil  is  contained  in  an 
airtight  receptacle  of  one-quart  capacity,  whence  it  is  led  to  the 
wheel  flanges  by  pipes  and  sprayed  upon  the  flanges  by  jets  of  air. 
The  air  is  supplied  through  a  J4-in.  pipe,  which  is  connected  to 
the  oil  receptacle  above  the  surface  of  the  oil.  A  branch  of  this 


ELECTRIC  STREET  AND  RAIL  CARS  285 

pipe  is  connected  to  the  oil  delivery  pipe  which  leads  to  the  flanges. 
The  air  is  controlled  by  an  electric  push  button,  so  that  the  lu- 
bricant is  applied  only  when  needed,  as  on  curves.  This  appara- 
tus has  been  in  successful  operation  since  July  10,  1910.  The 
six  electric  locomotives  to  which  it  has  been  applied  haul  1,000- 
ton  trains  up  and  down  2-per  cent,  gradients  on  which  flange  wear 
had  been  rather  heavy,  owing  to  the  many  curves  and  the  rather 
low  centre  of  gravity  of  the  locomotives.  Lubrication  of  the 
flanges  has  so  improved  conditions  that  50,000  miles  and  more 
are  now  run  between  wheel  tyre  turnings.  This  means  that  the 
wheels  can  be  removed  for  turning  at'the  same  time  that  the  arma- 
ture is  removed  for  commutator  dressing.  The  former  mileage 
made  between  tyre  turnings  was  from  12,000  to  25,000  miles. 
Filtered  reclaimed  armature  bearing  oil  is  the  lubricant  used. 


CHAPTER  XX 


TRANSMISSION  SHAFTING 

The  long  main  lines  of  shafting  used  for  power  transmission 
are  called  line  shafting.  Countershafting  is  driven  from  the  line 
shafting  and  operates  the  various  machines  by  fast  and  loose 
pulleys  or  by  clutches. 

The  speed  of  shafting  ranges  from  120-450  R.P.M.;  the 
diameter  of  line  shafting  usually  ranges  from  2J/£  in.  to  6  in.,  of 

countershafting  from  1  in.  to  2J^ 
in. 

Many  bearings  on  countershaft- 
ing and  small  diameter  line  shaft- 
ing are  hand  oiled  or  oiled  by  glass 
bottle  oilers.  Line  shafting  bear- 
ings are  seldom  hand  oiled;  they 
are  usually  bottle  oiled  and  modern 
shafting  is  frequently  ring  oiled. 
Ball  and  roller  bearings  are  also 
coming  into  prominence  for  quick 
speed  line  shafting. 

Heavy  large  diameter  shafting 
bearings,  as  for  example  many 
second  motion  shaft  (jack  shaft) 
bearings,  develop  so  much  heat 
that  they  can  be  kept  cool  only 
by  a  circulation  oiling  system. 
,,  Fig.  114  shows  a  simple  form. 

JIG.    114. — Screw-circulation  oiling.  .    ^ 

The  screw  can  be  lifted  right 
out  for  examination  by  taking  hold  of  the  knob. 

Fig.  115  shows  a  more  elaborate  system  with  three  oil  feeds 
from  the  oil  box.  The  drawing  will  need  no  explanation. 

The  power  required  to  drive  the  line  and  countershafting  in  a 
mill  or  shop  is  always  a  considerable  percentage  of  the  total  load. 
In  textile  mills  it  ranges  from  20  per  cent,  to  60  per  cent.;  in 
engineering  workshops  it  ranges  from  20  per  cent,  to  75  per  cent. 
Whether  more  or  less  machines  are  in  operation,  the  shafting 
load  is  always  of  the  same  magnitude,  and  it  is  not  too  much  to 
say  that  in  most  existing  factories  or  works  an  average  of  10 

286 


TRANSMISSION  SHAFTING 


287 


per  cent,  could  be  saved  in  the  shafting  load  by  introducing  better 
lubricants,  and  another  10  per  cent,  by  regular  attention  to 
keeping  the  shafting  in  perfect  alignment.  Losses  from  poor 
alignment  and  from  unsuitable  oils  frequently  occur  simul- 
taneously. Poor  alignment  often  means  that  certain  bearings 
heat  due  to  the  extra  load;  instead  of  the  bearings  being  adjusted, 
the  oil  gets  the  blame  and  a  more  viscous  shafting  oil  is  introduced, 
which  " cools"  the  bearings  inclined  to  heat  and  at  the  same  time 
adds  10  per  cent,  to  25  per  cent,  of  extra  fluid  friction  to  all  the 
other  bearings.  If  bearings  are  kept  in  good  alignment,  low 


FIG.   115. — Pump  circulation  oiling. 

viscosity  shafting  oils  can  be  used  and  a  considerable  saving  in 
power  obtained  (see  remarks,  page  312,  regarding  shafting  in 
textile  mills). 

Where  electric  driving  is  employed,  it  is  a  simple  matter  to  take 
the  shafting  load  every  3  or  6  months,  as  a  check  on  the  efficiency. 
With  steam  plants,  the  I.H.P.  may  be  recorded,  or  the  number  of 
revolutions  of  the  flywheel  and  the  time  taken  before  it  comes  to 
rest  from  full  normal  speed,  after  steam  has  been  shut  off. 

Shafting  bearings  should  be  provided  with  savealls  to  prevent 
dripping  of  lubricant.  Oil  creeping  along  the  shaft,  when  it  does 


288 


PRACTICE  OF  LUBRICATION 


occur,  is  usually  only  toward  one  side  of  the  bearing,  and  may  be 
overcome,  as  shown  in  Fig.  116  by  an  oil  thrower  (1)  and  splash- 
guard  (2).  The  oil  drops  from  the  splashguard  into  the  saveall 
(3).  As  regards  ring  oiling  bearings  see  pp.  158. 

Ball  and  roller  bearings  save  a  great  deal  of  power;  a  type  of 
roller  bearing  very  suitable  for  line  shafting  is  the  Hyatt  flexible; 
roller  bearing , (Fig.  53,  page  177)  which  gives  a  coefficient  of 
friction  of  .005  to  .008,  whereas  ball  shafting  bearings  give  a 
coefficient  of  friction  of  .002  to  .003.  Good  alignment  is  essential 
with  ball  and  roller  bearings,  more  so  than  with  plain  bearings, 
an  exception  being  the  Skefko  Ball  Bearing.  The  following 


FIG.   116. — Shafting  oil  thrower. 

figures  indicate  the  coefficient  of  friction  which  may  be  expected 
for  different  methods  of  lubrication  in  connection  with  shafting 
bearings. 

Coefficient  of  friction 

Ball  bearings ..." 002-.  003 

Roller  bearings 

Ring  oiling  bearings 

Bottle  oiling,  syphon  oiling 

Hand  oiling 


.005-. 008 
.010-. 015 
.02  -.04 
.04  -.15 


The  great  savings  in  power  which  follow  the  introduction  of 
high-class  shafting  bearings  is  better  realized  on  the  Continent  of 
Europe  than  elsewhere;  in  Great  Britain  and  the  United  States 
conditions  of  shafting  are  much  behind  Continental  practice. 


TRANSMISSION  SHAFTING  289 

Lubrication.  Most  shufting  bearings  -are  lubricated  l)y  oil; 
as  mentioned  elsewhere  shafting  in  weaving  sheds  is  frequently 
lubricated  by  grease  applied  through  gravity  grease  cups,  spring 
grease  cups,  or  applied  direct  to  the  shaft.  Stauffer  cups  are  not 
used  because  they  require  to  be  given  a  turn  every  day  or  two, 
while  the  other  methods  are  more  or  less  automatic  in  action  and 
require  attention  only  at  long  intervals. 

The  waste  in  power  by  applying  grease,  as  compared  with  oil, 
ranges  from  5  per  cent,  to  20  per  cent,  of  the  shafting  load,  accord- 
ing to  the  fluidity  and  quality  of  the  grease  and  the  speed  of  the 
shafting. 

The  better  the  lubricating  system  the  lower  viscosity  oil  can  be 
used,  and  the  lower  the  friction. 

For  hand  oiling,  oils  compounded  with,  say,  5  per  cent,  of  a 
non-gumming  fatty  oil  will  last  longer  and  give  better  results  than 
straight  mineral  oils.  For  bottle  oilers  straight  mineral  oils 
should  be  used  to  ensure  the  needles  keeping  clean  and  in  working 
order.  Oils  for  ring  oiling  bearings  and  ball  bearings  should  also 
be  straight  mineral. 

The  following  chart  is  a  rough  guide  for  selecting  the  correct 
grade  of  shafting  oil  • 

LUBRICATING  CHART  NO.  8 
FOR  SHAFTING  BEARINGS 

Rearing  Oil  No.  21 For  most  moderate  and  high  speed  shafting  and 

countershafting  in  good  alignment  and  condition 

and  with  reasonably  good  lubricating  appliances. 

This  oil  is  usually  too  thin  for  hand  oiled  bearings. 

Bearing  Oil  NQ.  3 For  slow  or  moderate  speed  light  and  medium 

shafting  and  countershafting  in  good  or  moder- 
ate condition  and  with  good  or  moderate  'lubri- 
cating appliances. 
Also  for  hand-oiled  bearings  on  countershafting. 

Bearing  Oil  No.  4 For  slow  or  moderate  speed,  heavy  shafting. 

NOTE. — Lubricants  for  Ball  and  Roller  Bearings  (see  page  190). 

Shafting  Greases Grease  should  be  of  as  light  a  consistency  and  as 

low  a  melting  point  as  practicable,  without  in- 
curring undue  waste  of  lubricant. 
The  mineral  oil  used  in  the  grease  should  be  of 
similar  viscosity  to  the  oil  which  would  prove 
suitable  if  the  bearings  wore  arranged  to  use  oil 
instead  of  grease. 

For  Bearing  oils,  see  page  127. 


CHAPTER  XXI 


MACHINE  TOOLS 

Machine  tools  are  machines  such  as  lathes,  shapers,  boring, 
drilling,  milling,  planing  and  grinding  machines,  etc.,  the  speeds 
ranging  from  quite  low  on  large  lathes  and  planers  to  very  high, 
up  to  10,000  to  30,000  r.p.m.,  for  modern  grinders. 

There  are  a  great  many  bearings  on  most  machine  tools  which 
are  hand  oiled,  the  speeds  or  pressures  being  low.  The  oil  holes 
should  preferably  be  protected  by  a  cover.  Fig.  117  shows  a 
typical  oil  hole  cover;  the  lid  (1)  is  turned,  disclosing  the  oiling 
hole  (2) ;  the  lid  by  means  of  an  internal  spring  may  be  made  to 


-2 


FIG.  117.— Oil  hole  cover.     FIG.  118.— Ball  valve      FIG.     119.— Oil    hole 

and  felt  chamber.  protector. 

Hand  oiling  arrangements. 

turn  back  automatically  and  cover  the  hole  after  the  oiling  opera- 
tion. Fig.  118  shows  a  hand  oiling  arrangement  with  ball 
valve  (1)  and  felt  chamber  (2).  Felt,  wool,  or  worsted  yarn  may 
be  used  in  the  chamber,  and  serves  to  feed  the  oil  more  uniformly 
to  the  bearing  in  between  oilings.  With  a  rise  in  temperature 
more  oil  is  liberated,  so  that  such  an  arrangement  is  a  great  im- 
provement over  the  ordinary  oil  hole  without  felt. 

Fig.  119  shows  a  simple  oil  hole  protector,  consisting  of  a 
cup,  the  shank  of  which  is  split  in  three  parts  which  grip  the  oil 
hole,  as  the  cup  is  pressed  into  position.  The  cup  and  shank  are 
filled  with  felt,  which  acts  in  the  same  way  as  the  felt  in  Fig.  118. 

In  many  modern  machine  tools  felt  pad  arrangements  are  made 
use  of  to  a  considerable  extent.  Fig.  120  shows  an  arrange- 
ment used  byBrownand  Sharpe  for  the  bearings  of  internal  grind- 

290 


MACHINE  TOOLS 


201 


ing   spindles.     The   oil   soaks  through  the  felt  and  enters  the 
bearing  through  the  passage  shown. 

In  many  bearings  large  recesses  are  cored  out  around  the  spin- 
dle boxes  in  the  middle  and  fitted  with  felt  pads  which  are  pressed 


LLJJ 

FIG.   120.  —  Felt  oiling  arrangement  for  grinder  spindle. 

gently  against  the  revolving  spindle  by  means  of  light  feather 
or  spiral  springs. 

'  Fig.  121  shows  two  types  of  pads;  when  in  use  they  are  both 
placed  below  the  spindles  in  a 
well  partly  filled  with  oil,  which 
is  replenished  from  time  to  time 
through  an  oil  filling  hole  at 
the  top  communicating  with 
the  oil  well.  Right-  and  left- 
hand  spiral  grooves,  as  shown 
in  Fig.  122  are  excellent  for 
distributing  the  oil  toward  the 
bearing  ends,  where  fine  V 
threads  on  the  spindle  cut  in 
the  opposite  direction  tend  to 
prevent  leakage  and  have 
proved  very  efficient  in  this 
respect. 


FIG.   121. — Spring  felt  pads. 


Bearings  which  require  a  fair  amount  of  oil  may  be  supplied  by 
small  syphon  oil  cups  or  drop  feed  oilers;  occasionally  ring  oiling 
bearings  are  employed.  In  some  recent  designs  a  circulation 
oiling  system  is  employed,  a  pump  delivering  the  oil  to  a  distri- 


292 


PRACTICE  OF  LUBRICATION 


bating  box  whence  oil  is  guided  to  the  various  bearings  and 
gears  and  finally  returns  to  the  pump  reservoir.  Grease  is  sel- 
dom used  for  machine  tools,  except  in  ball  bearings,  which  are 
now  widely  used,  especially  as  vertical  thrust  bearings  for  drill 
spindles,  heavy  revolving  tables,  etc. 

The  lubrication  of  lathe  saddles,  ram  slides  of  shaping  ma- 
chines, flat  or  V-shaped  slides  of  planing  machines,  is  receiving 
more  attention  nowadays.  Instead  of  the  surfaces  merely  being 
flooded  by  an  oil  can,  most  of  the  oil  being  wasted  to  no  good  pur- 
pose, some  modern  machines  have  felt  pad  insertions  in  the  sliding 
member.  The  felt  pads  are  kept  soaked  with  oil,  being  hand 


FIG.   122. — Spiral  oil  grooves  for  grinder  spindle. 

oiled  through  oil  passages  from  above,  and  keep  the  large  sur- 
faces economically  and  fairly  well  lubricated.  In  some  V-grooved 
slides,  V-shaped  wheels  are  placed  in  the  stationary  slides;  the 
wheels  are  partly  immersed  in  oil,  and  are  forced  gently  against 
the  moving  slide  which  they  lubricate.  The  felt  pad  arrangement 
is  probably  equal  to  if  not  more  efficient  than  the  revolving 
wheels. 

Apart  from  high  speed  machine  tools,  the  majority  of  bearings 
in  machine  tools  are  only  poorly  lubricated  at  the  best  of  times 
and  the  coefficient  of  friction  is  high.  Slightly  compounded  oils 
are  therefore  preferable  to  straight  mineral  oils,  as  they  have 
greater  oiliness.  The  low-viscosity  oils,  which  are  (or  ought  to 


MACHINE  TOOLS  293 

be)  used  for  high  speed  tools  like  grinders,  need  not  be  com- 
pounded, as  the  friction  depends  upon  the  viscosity  of  the  oil  and 
not  on  its  oiliness. 

Exposed  in  thin  films  to  the  oxidizing  influence  of  air  and  fine 
metallic  dust,  the  oil  which  invariably  creeps  all  over  the  machine 
tools  in  time  oxidizes  and  stains  or  tarnishes  the  bright  surfaces, 
particularly  in  machine  shops  exposed  to  bright  light  or  sunlight. 

In  all  mineral  oil  there  are  certain  complex  unsaturated  hydro- 
carbons, coloring  matter,  etc.,  which  are  easily  oxidized  and  which 
arc  the  cause  of  the  brown,  thin,  tenacious  films  just  referred  to. 

Pale  mineral  oils  are  less  apt  to  cause  tarnishing  than  dark 
colored  oils,  and  it  is  a  great  help  to  have  a  few  per  cent,  of 
animal  oil,  say  6  per  cent,  of  lard  oil,  mixed  with  the  mineral  oil. 
The  admixture  of  animal  oil  has  a  marked  effect  in  preventing  the 
oxidized  matter  from  forming  a  film,  and  makes  it  quite  easy  to 
wipe  the  surfaces  clean. 

An  admixture  of  a  vegetable  oil  will  have  the  opposite  effect;  it 
helps  to  cement  the  oxidized  matter  together  and  makes  it  more 
difficult  to  keep  the  bright  surfaces  on  the  machines  clean. 

LUBRICATION  CHART  NO  9 
FOR  MACHINE  TOOLS 

Oils  of  three  viscosities  are  required  as  follows : 
Bearing  Oil  No.  V For  very  high  speed  machines,  as  grinders. 

(Straight  mineral.) 
Bearing  Oil  No.  2 For  all  moderate  or  high  speed  machine  tools  of 

(Preferably  pale  and       every  description,  except  grinders. 

compounded  with  6 

per  cent,  of  lard  oil.) 
Bearing  Oil  No.  4 For  all  slow  or  moderate  speed,  heavy  machine 

(Preferably  pale  and       tools,  for  gear  chambers,  etc. 

compounded    with    6 

per  cent,  of  lard  oil.) 

1  For  Bearing  oils,  see  page  127. 


CHAPTER  XXII 
TEXTILE  MACHINERY 

The  textile  industries,  comprising  the  cotton,  woollen,  worsted, 
silk,  flax,  hemp  and  jute  industries,  are  all  highly  specialized  and 
employ  such  a  variety  of  machinery  that  it  is  impossible  inside 
a  few  pages  to  give  even  an  outline  of  the  principal  types  and  their 
uses. 

Characteristic  of  most  of  the  machines  is  that  the  amount  of 
power  actually  used  in  doing  useful  work,  that  is  in  handling  the 
fibres  or  material  itelf,  is  small  and  that  by  far  the  greater  por- 
tion of  power  is  consumed  -by  the  friction  of  numerous  spindles 
or  shafts  often  revolving  at  high  speeds  and  usually  only  lightly 
loaded. 

Great  improvements  have  taken  place  so  far  as  the  mechanical 
construction  and  lubricating  arrangements  are  concerned,  and 
the  author  will  endeavor  in  the  following  pages  to  point  out 
some  of  the  important  features.  While  some  considerable  atten- 
tion has  been  paid  to  the  selection  of  suitable  oils,  yet  very  great 
power  reductions  can  be  accomplished  in  practically  all  existing 
mills  by  the  introduction  of  such  oils  as  will  be  mentioned  later 
on. 

The  subject  will  be  divided  into  four  sections,  namely: 

1.  Preparing. 

2.  Spinning. 

3.  Weaving. 

4.  Bleaching,  Dyeing,  Printing  and  Finishing. 

PREPARING  MACHINERY 

Openers  and  Scutchers.  (Used  for  Cotton  Only). — Openers 
and  scutchers  are  very  similar  in  action;  they  open  and  loosen 
the  fibres  of  cotton  by  quickly  revolving  beaters;  the  cotton  fluff 
thus  formed  is  blown  a  certain  distance  and  again  gathered  to- 
gether, forming  a  soft  thick  sheet  of  cotton  called  a  lap.  In  this 
process  the  cotton  fibres  are  cleaned  from  dirt  and  grit,  passing 
first  through  the  openers  and  next  through  the  scutchers.  There 
are  quickly  revolving  spindles  in  these  machines,  the  lubri- 
cation of  which  is  important.  By  feeling  these  bearings  an 

294 


TEXTILE  MACHINERY 


295 


expert  cun  always  get  an  idea  of  the  quality  of  the  spindle  oil 
used  in  a  mill;  if  they  run  excessively  warm,  the  oil  in  use  is 
probably  too  viscous,  assuming  of  course  that  the  bearings  are 
in  good  condition  mechanically. 

The  high  speed  bearings  are  either  oiled  by  bottle  oilers  or 
they  are  preferably  ring  oiled. 

The  room  in  which  the  openers  and  scutchers  are  placed  is 
called  the  Blowing  Room  or  Scutching  Room. 

Washing  and  Drying  Machines.  —  (Used  only  for  wool  and 
worsted.)  Wool-washing  and  drying  machines  do  not  present 
any  lubrication  features  of  interest,  except  that  in  some  mills 
hydroextractors  are  used  for  "whizzing"  the  wool  before  it  passes 
into  the  drying  machines  for  the  final  drying. 

These  hydroextractors  are  of  the  same  type  as  those  used  for 
recovering  oil  from  waste  (Fig.  220,  page  566),  and  unless  they 


I  >     /       / 

/JJLIII  LI  LI  JJ.  JJ  UfJ  l/iiUiyj-J 

r      •«•—  /^  ? 


FIG.  123. — Preparer  gill  box. 

have  ball  bearings  or  Michell  bearings  they  require  oils  of  great 
oiliness,  much  more  viscous  than  the  spindle  oils  used  in  the  mill. 
Hydroextractors  are  usually  driven  direct  by  a  small  steam  en- 
gine or  steam  turbine. 

Preparer  Gill  Boxes. — (Used  for  wool,  worsted,  flax,  hemp, 
jute  and  waste  silk.)  These  machines  comb  open  the  fibres, 
lay  them  parallel  and  deliver  thefi  in  the  form  of  a  continuous 
"end"  or  "lap."  There  are  always  several  sets  of  gill  boxes 
through  which  the  material  has  to  pass. 

The  last  preparer  gill  box  in  the  series  is  called  the  can  gill  box 
and  is  shown  in  Fig.  123.  The  lap  (1)  enters  the  back  rollers 
(2),  is  drawn  between  the  front  rollers  (3)  and  delivered  through 
the  slowly  revolving  funnel  (4)  as  a  continuous  sliver  into  the 
can  (5).  Between  the  front  and  back  rollers  the  fibres  are 
combed  by  the  fast  moving  fallers  (6)  which  rest  with  their  ends 


206  PRACTICE  OF  LUBRICATION 

on  slides  and  arc.  pushed  to  the  right  by  means  of  square  threaded 
screws;  they  fall  at  the  end  and  are  returned  quickly  by  bottom 
screws  (revolving  in  the  opposite  direction)  to  be  raised  again 
into  position  just  behind  the  front  rollers. 

The  fallers,  slides,  screws,  etc.,  wear  rather  quickly,  and  good 
lubrication  is  therefore  extremely  important,  particularly  when 
working  with  dusty  fibres,  such  as  jute  and  hemp.  The  dust, 
which  is  composed  of  earthy  particles,  also  small  pieces  of  woody 
and  fibrous  matter,  contaminates  the  oil  on  all  rubbing  surfaces. 

If  when  leaving  the  gill  boxes  the  fibres  (such  as  wool)  go  to 
the  carding  machines,  they  must  be  oiled.  The  oiling  should  not 
be  done  in  the  first,  second,  or  third  gill  boxes,  but  preferably 
in  the  can  gill  box.  One  method  of  oiling  is  shown  in  Fig.  123. 
A  circular  brush  (7)  revolves  in  the  oil  trough  (8).  When  the 
bristles  of  the  brush  pass  the  blade  (9)  they  shower  or  spray  the 
hot  oil  onto  the  fibres  of  the  wool  as  they  pass  through  the 
machine. 

Carding  Machines. — (Used  for  all  short  fibres,  not  for  long 
worsted  and  long  silk).  The  carding  operations  remove  all  im- 
purities and  arrange  the  fibres  parallel,  delivering  the  material 
in  the  form  of  sliver. 

The  soft  laps  coming  from  the  blowing  room  enter  the  carding 
machine  and  are  broken  up  by  the  revolving  cards,  being  de- 
livered from  a  large  carding  drum  to  smaller  carding  drums  which 
return  the  fibres  to  the  main  drum ;  finally  the  fibres  are  removed 
in  the  form  of  a  thin  veil  from  the  last  drum  by  means  of  a  quickly 
oscillating  stripping  comb.  The  veil  is  gathered  together  through 
a  trumpet,  passes  a  pair  of  rollers  and  is  delivered  as  sliver  into 
a  card  can. 

The  bearings  for  the  stripping  comb  are  placed  in  so-called 
stripping  comb  boxes,  which  contain  a  bath  of  oil,  and  in  which 
cams  operate  and  give  motion  to  the  stripping  comb.  These 
stripping  comb  boxes  are  always  rather  warm  and  indicate  the 
quality  of  the  spindle  oil.  The  numerous  bearings  on  the  carding 
machines  require  to  be  well  oiled.  Several  of  the  spindles  sup- 
porting the  smaller  carding  dlums  have  an  endwise  oscillating 
motion,  tending  to  scrape  off  the  oil  film. 

There  are  usually  two  or  more  sets  of  cards  before  the  sliver 
is  passed  on  to  the  Drawing  Department. 

Short  wool  does  not  leave  the  cards  as  sliver,  but  before  going 
to  the  drawing  frames,  it  is  passed  fom  the  cards  straight  into 
so-called  condensers;  the  wool  enters  these  as  a  thin  soft  sheet 
and  is  divided  into  a  number  of  strips,  which  are  rolled  into  coarse 
threads,  suitable  for  coarse  spinning,  which  is  the  next  operation. 


TEXTILE  MACHINERY  297 

Combers. — (Used  for  all  long  fibres,  only  rarely  for  cotton.) 
Long  wool,  worsted,  flax  and  other  long  fibres  are  not  carded, 
but  pass  through  combers.  There  are  many  types  of  combers, 
but  the  object  in  them  all  is  the  same,  i.e.,  to  straighten  the  fibres 
and  separate  the  short  fibres  from  the  long  ones. 

Most  parts  of  these  machines  revolve  slowly,  such  as  revolving 
tables,  drawing  off  rollers,  etc.,  and  require  a  rather  viscous  oil, 
but  the  "dabbing  brushes"  have  a  quick  motion  and  should 
preferably  use  thin  spindle  oil.  Modern  dabbing  motions  are 
enclosed  in  a  chamber  containing  oil  to  ensure  continuous  lubri- 
cation and  a  speed  of  800-1200  dabs  per  minute  can  be  obtained 
without  unreasonable  vibration. 

The  slowly  revolving  tables — called  circles — are  often  sup- 
ported by  balls  placed  in  ball  races.  These  races  get  very  hot, 
when  the  circles  are  steam  heated,  and  the  oil  will  carbonize  and 
gum  unless  the  oil  manufacturer  has  kept  this  condition  in 
mind  and  selected  a  "non-carbonizing"  oil.  Some  circles  are 
supported  by  large  rollers,  which  revolve  and  dip  into  oil  reser- 
voirs and  are  thus  kept  continuously  oiled. 

Drawing  Frames.— The  drawing  frame  receives  thick  "slivers" 
of  fibres  and  attenuates  them  by  the  so-called  drawing  operation. 

The  frame  consists  essentially  of  several  sets  of  rollers,  each 
successive  pair  revolving  at  a  greater  speed  than  the  previous 
pair.  The  top  rollers  are  weighted  and  the  bottom  rollers  fluted 
to  grip  the  fibres  tightly. 

When  drawing  material  like  wool  or  worsted  the  rollers  are 
heavily  pressed  together,  and  a  specially  viscous  oil  is  required; 
with  cotton  the  rollers  are  not  so  heavily  loaded  and  they -are 
easier  to  lubricate.  Care  must  be  taken  not  to  overlubricate,  as 
if  the  oil  gets  on  the  rollers  it  will  produce  oil  stains  on  the  yarn. 
The  bearing  keeps  for  the  roller  bearings  should  preferably  be 
fitted  with  flannel  layers  inside,  which  have  the  effect  of  holding 
and  distributing  the  oil  all  over  the  bearing  surfaces  and  keeping 
the  dust  out. 

Slabbing,  Intermediate  and  Roving  Frames. — Slubbing,  inter- 
mediate, and  roving  frames  are  used  for  producing  coarse  thread 
from  the  sliver  coming  from  the  drawing  frames,  the  sliver 
passing  through  several  of  these  framed  in  the  order  indicated. 
Slubbing  and  intermediate  frames  are  used  only  in  cotton  mills; 
for  other  fibres  only  roving  frames  are  used. 

All  of  these  frames  are  flyer  frames  and  very  similar  in 
construction. 

Fig.  124  shows  a  slubbing  frame.  The  sliver  passes  from  the 
can  (1)  through  draft  rollers  (2)  through  the  hollow  arm  of  the 


298 


PRACTICE  OF  LUBRICATION 


flyer  (3)  and  is  wound  on  to  the  bobbin  (4)  driven  by  skew  wheels 
(5)  at  a  slightly  lower  speed  than  the  flyer,  which  is  driven  by 
skew  wheels  (6).  The  bobbin  together  with  its  wheel  drive  is 
continuously  lifted  and  lowered  during  the  operation. 

The  spindle  has  a  footstep-bearing  and  a  neck  bearing,  both 
usually  oiled  by  hand. 

2 


FIG.   124. — Slabbing  frame. 

SPINNING 

The  object  of  spinning  is  to  draw  out  and  twist  the  coarse 
thread  received  from  the  Preparing  Department  and  produce  a 
more  or  less  finely  spun  yarn.  There  are  four  main  types  of 
frames,  namely,  Ring  Frames,  Flyer  Frames,  Cap  Frames,  and 
Mule  Frames. 

Ring  Frames. — Figs.  125  and  126  show  this  type  of  frame  and 
spindle.  The  thread  is  drawn  by  the  draft  rollers  (2)  from  the 
bobbins  (1)  and  delivered  through  the  eye  (3)  to  the  bobbin  (4). 
The  bobbin  (4)  is  driven  from  the  tin  roller  (5),  pulls  the  thread 
through  the  " traveller"  (6),  and  continuously  winds  up  the 
yarn.  The  traveller  revolves  on  the  ring  (7)  fixed  on  the 
lifter  (8). 

The  bobbin  is  fixed  on  the  spindle  (9)  which  is  surrounded  by 
a  sleeve  and  immersed  in  an  oil  bath.  There  are  several  holes 


TEXTILE  MACHINERY 


299 


provided  in  the  sleeve  which  allow  the  oil  to  enter  freely  at  the 
bottom  and  the  side.  Some  of  the  oil  rises  along  the  spindle, 
overflows  at  the  top  and  returns  through  a  vertical  passage  to  the 
oil  reservoir  at  the  bottom. 

The  casing  and  oil  reservoir  in  which  the  spindle  revolves  is 
called  the  bolster.  '  It  will  be  noticed  that  the  spindle  sleeve  is 
provided  with  a  spring  which  will  allow  slight  lateral  movements 
of  the  sleeve  in  relation  to  the  bolster. 

"Make  up"  oil  is  added  at  intervals  through  the  oil  well  (10) 
which  communicates  with  the  bottom  oil  reservoir  and  is  pro- 
tected from  dust  due  to  the  shape  of  the  driving  whorl  (11). 


FIG.  125. — Ring  frame. 


FIG.     126.— Flexible    ring 
spindle. 


The  so-called  Rabbeth  spindles  are  now  going  out  of  use;  they 
are  similar  to  Fig.  126  except  that  the  spindle  sleeve  is  rigidly 
fixed  in  the  bolster.  They  cannot  be  operated  at  higher  speeds 
than  6,000  r.p.m.  as  they  are  then  inclined  to  throw  off  the  bob- 
bins. The  flexible  type  ring  spindles  are  operated  smoothly 
at  speeds  ranging  from  6,000  to  11,000  R.P.M.  notwithstanding 
slight  unevenness  in  the  driving  bands. 

When  a  new  frame  is  being  started  the  oil  should  be  pumped  out 
after  two  days'  working  and  fresh  oil  introduced.  The  oil  should 
be  renewed  after  a  week's  run  and  again  after  four  weeks'  further 


300 


PRACTICE  CXF  LUBRICATION 


running.  Current  practice  for  oiling  frames  afterward  is  to  add 
a  little  fresh  oil  every  three  months  to  the  oil  wells  and  to  empty 
them  for  cleaning  and  recharging  once  every  twelve  months. 

Fig.  127  shows  an  oil  can  for  refilling  spindle  baths.  The 
measure  (1)  is  lowered  in  the  tube  shown,  filled  with  oil,  and  when 
lifted,  tips  over  its  contents  into  the  spout  (2)  which  pours  the 
oil  into  the  spindle  bolster. 

Another  type  of  oil  can  is  also  used  for  this  purpose,  in  which 
there  is  a  plunger  pump  which  is  pressed  down  by  the  thumb. 
An  adjusting  screw  is  fixed  below  the  thumb-piece  by  means  of 
which  the  amount  of  each  discharge  can  be  adjusted.  The 
delivery  spout  may  have  a  sight  feed  arrangement  to  indicate 
that  the  pump  is  in  working  order. 

By  connecting  all  the  bolsters  to  a  horizontal  oil  pipe  (Fig. 
128)  and  having  an  oil  filling  vessel  (1)  at  the  end,  the  oil  level 


FIG.  127.— Ring  spindle  oil  can.     FIG.   128. — Ring  spindle  oiling  arrangement. 

is  correctly  maintained  for  all  spindles.  The  oil  level  cannot 
become  too  high,  because  of  the  overflow  (2)  which  discharges 
excess  oil  into  the  small  oil  receiver  (3).  The  system  can  be 
drained  by  removing  drain  plug  (4) . 

While  this  system  is  excellent  for  preventing  shortage  of  oil 
in  the  bearings,  it  carries  with  it  the  danger  of  forgetting  to  over- 
haul and  clean  the  spindles,  which  is  important  and  ought  to  be 
done  at  least  once  per  annum. 

Flyer  Frames.— (Used  for  all  fibres.)  Fig.  129  illustrates  a 
typical  Flyer  Spindle.  The  Flyer  (1)  revolves  and  lays  the  yarn 
on  the  bobbin  (2)  which  is  lifted  and  lowered  by  the  lifter  (3). 
The  spindle  is  supported  by  a  neck  bearing  (4)  in  the  rail  (5),  and 
a  footstep  bearing  (6). 

The  small  recess  shown  in  the  centre  is  not  often  found  in 
spindle  footstep  bearings,  but  is  a  great  advantage;  it  prevents 
heating  of  the  spindle  tip  and  serves  to  collect  dirt  which  other- 


TEXTILE  MACHINERY 


301 


wise  would  cause  friction  and  wear.  On  very  heavy  spindles  it 
would  probably  be  beneficial  to  let  the  oil  circulate,  as  indicated  in 
Fig.  129,  the  action  being  the  same  as  in  ring  spindle  footsteps. 

Flyers  used  for  wet  spinning  (flax  mills)  should  have  their 
tops  enclosed,  as  shown  in  Fig.  130,  to  prevent  entrance  of 
moisture,  which  causes  rusting  and  makes  it  difficult  to  unscrew 
the  flyers,  unless  a  heavily  compounded  oil  is  used  for  oiling  the 
spindle  tops. 

Fig.  130  shows  a  patent  flyer  spindle  (the  Bergmann  Spindle) 
used  for  spinning  flax,  hemp,  and  jute.  The  spindle  is  driven 
in  the  usual  manner  but  the  whorl  is  in  line  with  the  footstep, 


FIG.   129. — Flyer 
spindle. 


FIG.   130. — Bergmann 
spindle. 


FIG.  131. — Cap 
spindle  with  felt 
pad  oiling. 


so  that  the  principal  object  of  the  neck  bearing  is  to  steady  the 
spindle.  The  neck  bearing  is  made  very  flexible  by  means  of 
feather  springs  (1)  and  is  covered  with  a  lid  to  keep  out  dirt  and 
fluff  from  the  felt  oil  pad  which  keeps  the  spindle  well  oiled.  The 
whorl  protects  the  footstep  from  dirt,  and  in  this  type  of  footstep 
the  oil  may  be  arranged  to  circulate  in  the  same  way  as  in  the 
footsteps  of  ring  spindles.  If  the  spindle  is  lifted  by  means  of 
the  whorl,  the  footstep  bearing1  is  disclosed  for  examination  and 
oiling. 

The  felt  pad  arrangement  here  shown  (2)  and  also  used  for 
many  cap  spindles  (Fig.  131)  ought  to  be  much  more  widely 


302  PRACTICE  OF  LUBRICATION 

used  for  neck  bearings  of  flyer  spindles;  it  is  simple,  efficient 
and  economical. 

An  attempt  has  been  made  to  introduce  oil  circulation  for  the 
neck  bearings.  The  rail  is  hollowed  out  and  forms  an  oil 
reservoir;  the  oil  passes  slowly  through  tiny  openings  in  the  neck 
collars  into  the  neck  bearings;  by  means  of  collars  on  the  spindles 
below  the  rail  the  oil  is  thrown  off  into  dishes  surrounding  the 
spindle,  returning  through  pipes  to  an  oil  reservoir,  whence  a 
pump  takes  the  oil  and  delivers  it  into  the  rail.  The  oil  thus 
circulates  continuously.  It  should  be  drawn  off  every  three 
months  and  filtered,  and  can  be  used  again,  if  of  good  quality. 
This  arrangement  is,  however,  rather  complicated  and  not  so 
foolproof  as  the  felt  pad  arrangement. 

One  type  of  flyer  frame,  the  " Arnold  Forster"  frame,  has 
the  spindles  fitted  with  ball  bearings  and  a  self-lubricating  felt 
pad  to  ensure  smooth  and  easy  running. 

Cap  Frames. — (Used  for  wool,  worsted  and  waste  silk.) 
A  typical  cap  spindle  is  illustrated  in  Fig.  131.  The  spindle 
(1)  is  stationary  and  the  cap  (2)  rests  on  its  top.  The  bobbin  is 
revolved  by  means  of  the  whorl  (3)  operated  by  a  driving  band 
from  the  tin  roller.  The  bobbin  continuously  winds  up  the  yarn 
and  pulls  it  over  the  bottom  edge  of  the  cap.  The  lifter  (4)  raises 
and  lowers  the  bobbin,  which  slides  with  a  long  brass  tube 
(5)  on  the  spindle. 

Obviously,  it  is  very  important  to  oil  this  tube  well;  the  felt 
pad  arrangement  (6)  is  very  efficient  and  economical,  it  being 
sufficient  to  oil  the  felt  pad  once  every  week  or  fortnight.  In 
many  cap  spindles  there  is  no  felt  pad,  and  the  spindle  is  dabbed 
once  or  twice  per  day  with  an  oily  brush;  this  old  fashioned 
method  means  a  higher  oil  consumption,  more  wear  and  about 
10  per  cent,  higher  power  consumption. 

Mule  Frames. — (Used  for  cotton,  wool  and  waste  silk). 
Fig.  132.  The  mule  spindles  (1)  are  placed  on  a  movable  car- 
riage (2)  which  during  the  spinning  period  moves  to  the  left, 
while  the  draft  rollers  (3)  draw  the  thread  from  the  bobbins  (4). 
When  the  carriage  moves  to  the  right  the  yarn  is  wound  on  the 
spindles,  the  fallers  (5)  moving  down  into  such  positions  as  to 
guide  the  yarn  correctly  on  to  the  spindles. 

Mule  spindles  have  a  neck  bearing  and  a  step  bearing,  the 
same  as  the  flyer  spindles,  the  only  difference  being  that  they 
are  placed  at  an  angle;  the  oil  is  therefore  inclined  to  be  thrown 
out  of  the  footsteps.  One  method  to  minimize  waste  of  oil  due 
to  this  cause  is  to  protect  the  footsteps,  as  for  example  with 
Jagger's  Footstep  Protector  shown  in  Fig.  133  which  has  proved 


TEXTILE  MACHINERY 


303 


very  useful.  It  also  protects  the  bearing  from  dirt  and  Huff, 
and  during  oiling  all  oil  is  caught  by  the  protector;  without  pro- 
tectors much  oil  often  runs  down  the  rail  and  is  wasted. 


FIG.  132. — Mule  frame. 


The  neck  bearings  are  oiled  once,  twice,  or  three  times  per 
day  according  to  operating  conditions  and  the  class  of  oil  in  use. 
The  footsteps  are  usually  oiled  the  same  number  of  times  per 
week,  as  the  neck  bearings  are  oiled  per  day. 


FIG.  133. — Jagger's  footstep  protector. 

In  the  centre  of  the  mule  is  situated  the'headstock,  from  which 
all  parts  of  the  frame  receive  their  motion,  and  it  is  regarded  as 
one  of  the  most  ingenious  and  complicated  machines  in  the  textile 
trade. 


304 


PRACTICE  OF  LUBRICATION 


Driving  bands  are  usually  made  of  cotton  and  are  affected 
by  the  moisture  in  the  air.  With  most  spinning  frames  the 
consumption  of  power  varies  approximately  1  per  cent,  for  every 
6  per  cent,  variation  in  the  relative  humidity  of  the  atmosphere 
in  the  spinning  room.  The. higher  the  relative  humidity  the 
more  the  bands  contract,  and  the  higher  the  power  consumption. 

With  some  modern  frames,  notably  cap  frames  and  jute 
spinning  frames,  the  driving  bands  have  their  tension  maintained 
uniform  by  means  of  weighted  tension  pulleys,  as  shown  for  a 
cap  frame  in  Fig.  134. 

The  tension  need  therefore  never  be  any  more  than  that 
required  for  driving  the  spindles  at  their  correct  speeds,  and 


FIG.   134. — Uniform  belt  tension  arrangement. 

humidity  has  no  influence  on  the  power  consumption.  A  higher 
spindle  speed  can  obviously  be  obtained  with  this  type  of  drive, 
and  as  the  spindles  are  never  subjected  to  excessive  strains  from 
the  band  pulls  their  lubrication  is  easier;  lower  viscosity  spindle 
oils  can  be  employed  with  confidence  and  the  power  consumption 
can  then  be  considerably  reduced  as  compared  with  frames 
employing  the  ordinary  type  of  band  drive. 

Thread,  Twine  and  Cord. — In  the  treatment  and  manufacture 
of  thread,  twine  and  cord  a  variety  of  light  machines  are  employed, 
such  as  doubling,  winding  and  gassing  frames,  reeling  machines, 
twisting,  twine  and  cord  machines,  thread  polishing  machines, 
balling  and  spooling  machines,  the  lubrication  of  which  presents 
no  striking  features. 


TEXTILE  MACHINERY  305 

Doubling  frames  have  either  flyer  spindles  or  ring  spindles. 
There  are  some  self-acting  doubling  frames  (Twiners)  very  similar 
to  mule  frames.  Some  winding  frames  employ  ring  spindles. 

Rope  making  machines  ;are  either  vertical  or  horizontal 
machines,  the  former  being  used  chiefly  for  large  cables. 

From  the  lubrication  point  of  view  these  machines,  which 
often  look  ponderous  and  complicated,  consist  essentially  of 
revolving  bobbins  and  are  not  difficult  to  lubricate. 

Wool  Oils  and  Batching  Oils. — Wool  oils  are  used  for  lubri- 
cating the  fibres  preparatory  to  the  carding  operation. 

With  all  high  class  wool  the  oil  must  at  a  later  stage  be  com- 
pletely removed,  as  otherwise  the  yarn  will  not  take  the  dye  prop- 
erly. Olive  oil  is  undoubtedly  the  best  grade  of  wool  oil.  It  is 
easily  removed,  but  is  expensive,  therefore  only  used  for  the 
highest  class  of  material.  Other  fixed  oils,  such  as  nut  oil,  lard 
oil,  etc.,  are  almost  as  good  as  olive  oil,  but  are  also  expensive. 
Wool  oleins  (produced  from  wool  grease)  and  various  fatty  acids 
(oleic  acids)  are  much  used  mixed  either  with  a  percentage  of 
other  fixed  oil  or  with  mineral  oil,  even  up  to  80  per  cent,  of  the 
latter.  The  lower  the  class  of  material  and  the  more  intense 
the  scouring  methods,  the  more  mineral  oil  can  be  used  in  the 
mixture,  without  running  undue  risk  of  having  trouble  in  the 
dyeing  of  the  yarn.  The  wool  oil  must  never  contain  more  than 
6  per  cent,  of  fatty  acid,  or  12  per  cent,  of  wool  olein  (which 
normally  contains  50  per  cent,  of  free  fatty  acid),  as  more  acid 
weakens  the  fibres  and  destroys  the  wires  on  the  carding  machines 
as  well  as  the  pins  of  the  preparing  and  combing  machines 

Rape  oil,  cottonseed  oil,  and  the  like  are  not  so  suitable, 
as  they  oxidize  and  produce  gumminess  and  deposits  in  the 
machines. 

Some  mineral  oil,  20  per  cent,  to  30  per  cent.,  should  always  be 
present  in  the  wool  oil,  wherever  permissible,  as  its  presence 
greatly  reduces  the  well-known  tendency  which  all  fixed  oils, 
particularly  vegetable  oils,  have  for  spontaneous  heating,  which 
has  been  the  cause  of  many  outbreaks  of  fire. 

Batching  oils  are  used  for  softening  the  fibres  of  flax,  hemp  and 
jute.  Low  viscosity  mineral  oils  are  generally  used,  and  occa- 
sionally mixtures  of  whale  oil  and  mineral  oils. 

WEAVING 

Winding,  warping  and  sizing  machines  prepare  the  yarn  for 
the  weaving  process.  The  lubrication  of  these  machines  calls 
for  no  comment. 

20 


306  PRACTICE  OF  LUBRICATION 

Looms. — There  is  an  immense  variety  of  looms,  from  small, 
quick-speed  cotton  or  silk  looms  to  large,  slow-speed  carpet  looms. 

The  function  of  all  looms  is  to  form  a  fabric  by  interlacing  warp 
and  weft  threads;  there  are  three  essential  movements  in  a  loom: 
Shedding,  Picking,  and  Beating  Up. 

Shedding  is  the  operation  of  dividing  the  warp  into  two  portions  for  inser- 
tion of  the  weft. 

Picking  is  the  operation  of  passing  the  shuttle  containing  the  weft  through 
the  opening  formed  in  the  warp. 

Beating  up  is  performed  by  the  reed  and  sley,  which,  through  the  action 
of  cranks  and  connecting  rods,  advance  and  recede  from  the  cloth  after 
each  "pick"  in  order  to  place  the  weft  threads  parallel  with  one  another. 

Picking  motions  are  called  Overpicks  or  Underpicks,  accord- 
ing to  whether  the  shuttle  receives  its  motion  from  an  arm  placed 
above  or  below  the  sley.  Overpick  is  generally  used  for  fast 
running  looms,  and  most  heavy  slow-speed  looms  have  the  under- 
picking  motion.  This  motion  is  cleaner,  as  oil  is  not  required 
about  its  parts  near  the  cloth,  and  is  therefore  preferable  for 
white  and  light  colored  goods,  on  which  oil  stains  show  up  more 
than  on  dark  colored  fabrics. 

The  shuttle  at  the  end  of  each  journey  is  arrested  by  running 
into  an  "eye"  made  of  buffalo  hide  and  fixed  in  the  shuttle  box; 
the  buffalo  hide  is  steeped  in  neatsfoot  oil  to  preserve  it  and  to 
minimize  wear  of  the  shuttlenose. 

The  shuttle  gets  its  motion  from  a  buffalo  hide  " picker"  slid- 
ing on  the  picker  spindle  and  connected  with  the  driving  arm  by 
means  of  a  leather  strap.  The  driving  arm  has  a  jerky  motion 
which  causes  the  picker  to  hit  the  shuttle  hard  and  send  it  across 
the  loom  to  the  shuttle  box  on  the  other  side.  The  driving  arm 
may  also  be  arranged  in  the  form  of  a  lever,  which  acts  on  the 
picker  direct. 

The  picker  spindle  is  lubricated  by  dabbing  it  at  intervals  with 
an  oily  brush.  There  is  a  patent  automatic  picker  spindle  lubri- 
cator in  use  on  overpick  looms,  consisting  of  a  small  pad  saturated 
with  oil  and  carried  by  an  arm  which  brings  the  pad  into  contact 
with  the  picker  spindle  at  each  forward  movement  of  the  sley, 
and  on  the  return  movement  again  makes  the  pad  recede,  to 
give  room  for  the  passage  of  the  picker. 

The  danger  of  oil  getting  onto  the  cloth  increases  with  the 
speed  of  the  loom.  The  speed  is  given  in  number  of  " picks"  per 
minute  and  ranges  from  240  picks  per  minute  for  narrow  looms 
and  fine  material  down  to  20  picks  per  minute  for  very  coarse 
goods;  for  most  woolen  or  worsted  cloths  the  picks  number  from 
60  to  70  per  minute. 


TEXTILE  MACHINERY  307 

With  quick  speed  looms  the  cranks  operating  the  reed  arid 
sley  are  apt  to  throw  oil  onto  the  fabric,  particularly  so  when 
the  bearings  are  overlubricated. 

In  velvet  looms  the  fabric  is  woven  over  a  number  of  long 
" needles/'  which  are  continuously  withdrawn  from  the  finished 
portion  and  inserted  again;  in  large  velvet  looms  it  is  an  advan- 
tage to  oil  these  needles  sparingly  with  "stainless"  oil. 

BLEACHING,  DYEING,  PRINTING,  FINISHING 

Bleaching  and  dyeing  departments  employ  comparatively  little 
machinery  requiring  lubrication.  The  most  important  machines 
from  our  point  of  view  are  probably  the  hydroextractors. 

Printing  machines  (calico,  thin  woolen,  linen,  jute)  are  usually 
hand  oiled,  the  same  as  other  printing  machines. 

The  Finishing  processes  are  very  varied. 

For  cotton  goods  the  main  operations  are:  Singeing,  raising, 
shearing,  brushing,  steaming,  starching,  calendering,  impreg- 
nating, breaking  down,  damping,  mangling,  moireing,  embossing, 
tentering  and  stretching,  doubling,  measuring  and  plaiting, 
marking,  and  pressing. 

For  woollen  and  worsted  cloth  the  main  finishing  operations  are : 
crabbing,  scouring,  milling,  singeing,  dyeing,  raising,  wet  rolling, 
tentering,  cutting,  brushing,  shrinking,  pressing. 

Again  here  hydroexir  actors  are  used  after  the  dyeing  process, 
and  most  of  the  machines  used  up  to  this  point  are  fairly  heavy, 
slow-speed  machines,  requiring  a  viscous  oil  for  lubrication.  In 
the  scouring  process  any  oil  stains  received  during  manufacture 
must  be  scoured  out;  in  the  subsequent  operations  extreme  care 
must  therefore  be  taken  to  avoid  oil  stains  and  "stainless"  oil 
should  be  used  for  lubrication  in  the  last  few  stages,  i.e.,  cutting, 
brushing  and  shrinking.  The  pressing  is  generally  done  in  a 
hydraulic  press. 

For  linen  cloth  the  following  finishing  operations  are  used;  crop- 
ping, washing,  tentering,  beetling,  calendering,  pressing. 

For  jute  cloth  the  finishing  processes  are  as  follows:  damping, 
cropping,  calendering,  folding. 

The  only  machines  calling  for  comment  are  the  calenders  of 
which  there  are  several  forms,  all  consisting  of  several  heavy 
rollers  called  press  bowls  placed  horizontally  in  a  strong  frame 
and  pressed  against  one  another  with  more  or  less  pressure 
either  mechanically  or  hydraulically. 

The  bearing  brasses,  top  and  bottom,  should  preferably  only 


308 


PRACTICE  OF  LUBRICATION 


touch  the  journals  over  an  arc  of  90°  to  120°  and  the,  edges  .should 
be  well  chamfered  to  facilitate  the  entrance  of  the  oil;  when  there 
are  a  number  of  bearings  one  above  the  other,  the  waste  oil  from 
one  bearing  should  be  guided  into  the  bearing  just  below,  and  so 
on.  Some  of  the  bowls  are  heated  by  steam  or  gas,  and  their 
journals  become  very  hot,  so  much  so  that  oil  cannot  be  used  and 
high  melting  point  greases  have  to  be  employed.  The  wear  of 
calender  bearings  is  often  very  considerable. 


OIL  CANS  AND  CABINETS 

As  most  oiling  in  textile  mills  is  hand  oiling,  it  is  extremely  im- 
portant to  have  the  oil  cans  in  good  condition  and  see  that  they 
are  maintained  with  small  spout  openings.  Some  oilers  are  in- 
clined to  cut  off  the  ends  of  the  spouts  to  make  the  oil  flow  more 
readily  and  the  result  is  a  great  waste  of  oil,  as  when  a  row  of 
spindles  is  oiled  the  spaces  between  the  spindles  are  oiled  as 


FIG.   135. — Oil  saving  devices. 

well  as  the  spindles.  The  oil  cans  should  be  so  adjusted  that 
as  the  oiler  goes  along  the  frame  at  a  regular  speed  a  drop  of  oil 
falls  into  each  bearing. 

Fig.  135  illustrates  two  methods  of  regulating  the  oil  flow 
from  the  oil  can.  The  top  illustration  has  an  inside  cone  with  a 
tiny  opening,  so  that  it  is  impossible  to  get  a  rapid  feed  of  oil 
from  the  end  of  the  oil  can  spout.  The  cone  cannot  be  interfered 
with  by  the  operatives  and  can  be  made  of  any  size  according  to 
the  requirements.  The  bottom  illustration  shows  the  orifice  of 
the  spout  itself,  soldering  a  strong  cap  on  to  the  end  with  an  open- 
ing of  say  J-^2  inch.  The  drawback  to  this  arrangement  is  that 
the  operatives  can  easily  cut  off  the  cap,  whereas  they  cannot 
interef ere  with  the  cone  arrangement  shown  in  the  other  drawing. 

It  is  a  great  advantage  to  have  in  each  of  the  spinning  rooms  a 
small  cabinet  holding  a  few  gallons  of  oil  sufficient,  say,  for  one 
week's  consumption.  The  cabinets  should  be  arranged  with  lids 
that  can  be  padlocked.  .A  small  oil  can  can  be  filled  from  the 


TEXTILE  MACHINERY  309 

cabinet  without  waste  and  the  oil  is  always  kept  clean.  Such 
.small  cabinets  can  be  used  for  conveying  the  oil  from  the  store 
room  into  the  various  departments. 

STAINLESS  OILS 

So-called  "stainless"  oils  have  several  times  been  referred  to. 
Really  stainless  oils  do  not  exist;  any  oil,  whether  pale  or  dark 
in  color,  whether  mineral,  vegetable  or  animal,  will  in  time  pro- 
duce a  visible  stain,  but  the  term  stainless  as  applied  to  textile 
practice  usually  means  that  during  the  scouring  or  washing  proc- 
ess which  most  fabrics  undergo,  oil  stains  will  disappear. 

Oil  stains  take  the  form  of  drops,  splashes,  or  streaks.  They  may 
be  due  to  oil  dropping  from  overhead  shafting,  or  oil  may  have 
got  on  to  the  yarn  due  to  over-oiling  the  top  roller  bearings  in 
the  spinning  frames.  Weavers  sometimes  cover  up  defects  by 
smearing  with  dirty  oil  to  escape  detection.  Oil  stains  have 
been  caused  by  greasing  the  reed,  but  the  most  frequent  cause  of 
oil  stains  is  oil  throwing  from  the  cranks  operating  the  sley  and 
from  the  cams  actuating  the  pickers;  such  splashes  show  up 
chiefly  on  the  warp.  Stains  are  also  caused  by  oil  splashes  from 
the  picker  spindle  in  the  shuttle  box.  Hence  the  reason  why  a 
stainless  picker  spindle  oil  is  nearly  always  used,  even  if  the  loom 
oil  employed  for  other  parts  of  the  loom  is  not  stainless. 

As  to  oil  dropping  from  overhead  shafting,  the  oil  stains  pro- 
duced are  often  difficult  or  impossible  to  remove,  owing  to  the 
presence  of  fine  metallic  wearings  in  the  oil,  chiefly  iron.  Iron 
stains  become  red;  copper  or  brass  stains  may  become  black,  gray 
or  greenish. 

Mineral  oils  give  a  permanent  stain  on  fabrics  and  the  darker 
the  oil,  the  more  objectionable  are  the  stains.  Even  bloomless 
oil  or  oils  so  pale  as  to  be  almost  water  white  will  in  time  become 
yellow,  due  to  oxidation,  and  the  color  will  continue  to  deepen 
with  time.  The  longer  the  interval  between  producing  the  stain 
and  the  attempt  to  remove  it  (scouring)  and  the  less  severe  the 
scouring  process,  the  less  oil  will  be  removed.  If  only  a  short 
time  has  passed,  stains  may  be  removed  by  dabbing  with  lard 
oil,  olive  oil  or  other  fixed  oil,  which  by  blending  with  the  mineral 
oil  makes  it  stainless,  i.e.,  it  can  be  removed  by  scouring  with  soda 
lye  in  the  ordinary  way. 

Cotton  cloths  are  bleached,  and  mineral  oil  stains  are  decom- 
posed in  this  process,  by  the  successive  attacks  of  alkali  and  chlo- 
rine. For  a  time  after  bleaching  the  oil  stains  will  not  appear, 
but  after  several  months,  the  stains  begin  to  show  up  yellow. 


310  PRACTICE  OF  LUBRICATION 

The  best  remedy  for  oil  stains  is  to  take  such  precautions  that 
no  oil  stains  are  formed.  In  many  weaving  mills,  shafting  is 
grease  lubricated  for  this  reason,  or  if  oil  is  used  for  the  bearings, 
they  are  well  fitted  up  with  splashguards  and  savealls,  which 
prevent  the  oil  dripping  from  bearings  or  creeping  along  the 
shafting  and  then  dropping. 

Where  it  is  considered  necessary  to  have  a  stainless  oil,  the 
degree  of  stainless  properties  required  depends  upon  the  length  of 
time  the  goods  are  stored  before  scouring  and  upon  the  severity 
of  the  scouring  operation.  Speaking  generally,  an  admixture  of 
15  per  cent,  of  good  quality  animal  oil  or  equivalent  non-drying 
fixed  oil  will  impart  to  the  spindle  or  loom  oil  sufficient  stainless 
properties  for  the  majority  of  conditions. 

In  cotton  mills  many  looms  require  stainless  oils  only  for  the 
picker  spindle. 

In  woollen  and  worsted  mills  stainless  loom  oil  should  be  used 
for  .lubrication  throughout  for  all  looms  weaving  high  class  cloth, 
as  dress  cloth,  or  such  cloth  as  is  used  for  naval  uniforms,  etc. 

For  low  woollen  goods,  blankets,  etc.,  stainless  oils  are  never 
required. 

In  linen  mills  stainless  oils  are  not  infrequently  used  for  high 
quality  goods,  but  in  jute  mills  stainless  oils  are  rarely  if  ever  called 
for,  as  the  material  is  not  of  sufficient  high  quality  to  justify  the 
extra  cost  of  stainless  oils  above  the  cost  of  ordinary  loom  oils. 

In  hosiery  factories  for  material  such  as  woollen  underwear, 
light  colored  stockings,  etc.,  stainless  oils  must  be  used  as  the 
fabric  invariably  gets  more  or  less  soiled  with  oil  during  manu- 
facture. This  point  is  so  important  that  many  hosiery  factories 
when  testing  the  oil  for  stainless  properties  soak  a  piece  of  fabric 
with  the  oil,  keep  it  in  stock  for  a  certain  time  and  then  scour 
it  to  see  whether  the  oil  can  be  entirely  removed. 

In  lace  and  curtain  factories  pure  neatsfoot  oil  is  often  used  as 
the  fabrics  receive  only  a  gentle  washing  and  the  oil  must  scour 
out  very  easily.  Not  infrequently  the  fabrics  are  not  washed  at 
all  and  it  is  then  absolutely  necessary  to  have  an  oil  as  pale  and 
as  stainless  as  possible. 

Neatsfoot  oil  meets  the  requirements.  It  is  almost  colorless 
and  even  if  there  are  oil  stains  on  the  lace  or  curtains  they  will  be 
removed  the  first  time  they  are  washed. 

In  many  special  industries  such  as  corset  manufacturing,  the 
thread  used  for  stitching  is  oiled  occasionally  in  order  to  lubricate 
the  needles  in  the  machines.  As  the  corsets  are  not  washed  the 
oil  must  be  as  pale  and  as  stainless  as  possible.  Again  here,  neats- 
foot oil  or  a  mixture  of  neatsfoot  oil  with  water-white  mineral  oil 


'TEXTILE  MACHINERY  311 

is  required.  If  there  is  a  considerable  percentage  of  mineral  oil 
in  the  mixture  the  oil  stains  will  in  time  become  yellow,  so  that 
for  white  goods  which  are  kept  in  stock  a  long  time  this  is  an  im- 
portant point  to  keep  in  mind. 

Table  No.  12  gives  the  author's  specifications  for  spindle  and 
loom  oils. 

TABLE   No.    12. — GRADES  OF  SPINDLE   AND  LOOM  OILS 


Saybolt 
viscosity  at 
104°F.,  sees. 

Per  cent,  of 
compound 

Spindle  oil 
Spindle  or 

No. 
loom 

1.. 

oil 

No 

2 

Up        55 
95 

Nil 
5-6 

Spindle  or 
Spindle  or 

loom 
loom 

oil 
oil 

No. 

No 

2S  
3 

95 
i         125 

15-20 
5-6 

Spindle  or 
Spindle  or 

loom 
loom 

oil 
oil 

No. 

No 

3S  
4 

125 

.    j         150 

15-20 
5-6 

Spindle  or 
Lather  oil 

loom 

oil 

No. 

4S  

150 
75-100 

15-20 
30-35 

As  to  the  nature  of  the  compound,  rape  oil  has  been  used  with 
success  but  the  oil  is  inclined  to  gum  and  tarnish,  particularly 
where  frames  or  machinery  are  exposed  to  sunlight.  With 
blown  rape  the  tendency  to  gum  is  still  greater;  animal  oils  have 
a  much  less  tendency  to  oxidize  and  should  be  preferred;  sperm 
oil  is  excellent,  but  very  expensive;  lard  oil  or  pale  whale  oil  will 
give  good  results;  if  desired  they  may  both  be  used  together  in 
the  same  spindle  or  loom  oil.  When  stainless  properties  are 
required  (Nos.  2S.,  3S.,  and  4S.)  a  small  percentage  ofolein,  say 
not  exceeding  3  per  cent.,  is  an  advantage,  as  it  has  good  emulsi- 
fying properties. 

The  mineral  base  of  the  oil  should  be  pale  in  color,  but  it  does 
not  matter  whether  it  is  an  acid  treated  or  .a  neutral  filtered  oil. 

Lather  oil  (see  page  315)  must  possess  exceptionally  good  stain- 
less properties;  it  must  therefore  be  made  from  pale  colored, 
preferably  water-white  mineral  oil  and  a  large  percentage  of  fixed 
oil,  say  30  per  cent,  to  35  per  cent.,  and  its  free  fatty  acid 
contents  must  not  exceed  5  per  cent.;  more  acid  will  cause 
trouble  with  rusting  of  the  needles  and  other  parts.  A  suitable 
lather  oil  may  be  made  from  24  per  cent,  rape,  6  per  cent,  pale 
whale,  3  per  cent,  olein  and  67  per  cent,  water  white  mineral  oil 
of  low  viscosity,  say  75"  to  100"  Saybolt  at  104°F. 

Each  factory  has  its  own  formula  for  lather  oil  mixture.  The 
following  is  typical : 


312 


PRACTICE  OF  LUBRICATION 


Lather  oil 3  gal. 

Hard  household  soap 7  Ib. 

Water 18  gal. 

LUBRICATION  OF  TEXTILE  MILLS 

Engine  Room. — Steam  engines,  chiefly  of  horizontal  construc- 
tion, are  largely  used  for  driving  textile  mills;  generally  they  drive 
the  various  mill  floors  by  rope-drives  from  the  flywheel.  In 
modern  mills  electric  driving  is  not  infrequently  used,  the  gen- 
erators being  operated  either  by  steam  engines  or 
turbines,  only  rarely  by  gas  engines. 

As  to  the  lubrication  of  these  engines  the  reader 
is  referred  to  .the  information  given  under  the  re- 
spective headings.  The  author  would  only  mention 
the  desirability  of  using  compounded  steam  cylinder 
oils,  and  using  a  lower  viscosity,  preferably  filtered 
cylinder  oil  in  the  large  low  pressure  cylinders. 

The  practice  of  using  very  viscous  oil,  even 
cylinder  oil,  on  the  guides  is  not  a  desirable  one; 
an  engine  oil  like  Bearing  Oil  No.  41  will  generally 
be  found  suitable  for  external  lubrication  through- 
out, as  well  as  for  the  second  motion  shaft  bearings 
(rope  race).  When  main  bearings  or  crank  pins 
are  difficult  to  keep  cool  with  this  oil,  Marine  Engine 
Oil  No.  1  or  2  may  be  recommended,  even  with  a 
gravity  circulation  system,  which  is  frequently  em- 
ployed in  textile  mills. 

Mill  Shafting. — The  shafting  generally  operates 
at  rather  high  speeds,  from  160  to  350  R.P.M.  and 
the  bearings  are  either  bottle  oiled  or  ring  oiled. 
The  countershafting,  gallow-pulleys,  etc.,  are  often 
hand  oiled.  As  such  hand  oiling  is  a  tedious  occupa- 
tion, it  not  being  easy  to  reach  the  bearings,  a  shaft- 
ing oiler  is  often  used,  as  illustrated  in  Fig.  136. 
By  pulling  the  trigger  (1)  the  piston  (2)  is  depressed  against  the 
action  of  a  spring  and  discharges  a  small  amount  of  oil  through 
the  feeding  tube  (3). 

In  many  mills  the  engine  oil  used  in  the  engine  room  is  also 
used  for  the  mill  shafting,  and  the  waste  in  power  caused  hereby 
is  on  the  average  4  per  cent,  of  the  full  mill  load.  The  engine 
and  shafting  load  (transmission  load)  is  approximately  25  per 
cent,  to  30  per  cent,  of  the  full  mill  load  and  the  saving  in  power 
by  introducing  Bearing  Oil  No.  2  which  the  author  recommends 
generally  for  mill  shafting,  is  roughly  15  per  cent,  of  the  transit,  is- 
1  See  page  127. 


FIG.  136.— 
Overhead 
shafting  oiler. 


TEXTILE  MACHINERY 


313 


sion  load.  It  is  ;i  rare  thing  to  find  shafting  oils  in  use  lower  in 
viscosity  than  Bearing  Oil  No.  3  and  against  this  oil  Bearing  Oil 
No.  2  will  save  about  10  per  cent,  on  the  transmission  load. 

Mill  Lubrication. — (Spinning  Mills).  Frequently  one  oil  is 
used  throughout,  except  for  ring  spindles,  which  are  always  given 
a  separate  oil,  similar  in  viscosity  to  Spindle  Oil  No.  2.  The  mill 
oils  used  are  generally  similar  in  viscosity  to  Bearing  Oil  No.  3  and 
occasionally  slightly  lower  in  viscosity,  but  seldom  below  150" 
Saybolt  at  104°F.  The  oils  are  often  straight  mineral,  but  some- 
times compounded  with  from  5  per  cent,  to  10  per  cent,  of  fixed  oil. 

The  author,  however,  recommends  Spindle  Oil  No.  3  for  general 
mill  lubrication  of  preparing  and  spinning  de- 
partments as  well  as  for  countershafting  and 
gallow  pulleys. 

For  ring  spindles,  Spindle  Oil  No.  1  is  recom- 
mended. For  high  speed  mules,  flyers,  and 
for  all  cap  spindles,  Spindle  Oil  No.  2  is  re- 
commended in  preference  to  Spindle  Oil  No. 
3  as  it  gives  an  even  greater  reduction  in 
power  [compared  with  the  oils  generally 
employed. 

When  the  spindle  bearings  begin  to  get  dry, 
the  spindles  "  whistle,"  vibrate  (" dance "), 
and  frequent  breakages  of  the  yarn  occur. 
With  compounded  oils  the  tendency  to  run 
dry  will  always  be  found  to  be  much  reduced, 
as  compared  with  straight  mineral  oils. 

Compounded  oil  must  not  be  used  for  ring 
spindles  as  in  time  it  will  produce  a  gummy 
deposit  which  will  interfere  with  lubrication, 
choking  the  vertical  passage  in  the  bearing. 
If  the  oil  is  of  too  low  viscosity  or  badly  re- 
fined it  will  cause  continuous  wear  on  the  step  bearing,  so  that 
notwithstanding  repeated  cleaning  the  oil  will  always  become 
discolored. 

The  pump  illustrated  in  Fig.  137  is  used  for  the  purpose  of 
extracting  old  oil  from  bath  spindle  bearings  before  they  are 
cleaned  and  re-oiled.  The  pipe  is  inserted  in  the  spindle  bearing; 
the  piston  is  operated  up  and  down  by  the  handle,  drawing  the 
dirty  oil  out  from  the  bearings  and  discharging  it  into  the  main 
barrel  of  the  pump  which  can  afterward  be  emptied. 

In  wet  flax  spinning,  a  special  oil  must  be  used  for  oiling  the 
flyer  spindle  tops,  when  they  are  of  the  open  type,  say  spindle 
oil  No.  4S.  Many  mills  use  lard  oil  or  olive  oil,  but  these  oils 
arc  unnecessarily  expensive  and  no  better  than  the  oil  just  men- 


FIG.  137. 


314  PRACTICE  OF  LUBRICATION 

tioned.  The  advantage  of  compounded  oils  over  straight  min- 
eral spindle  oils  are  that  lower  viscosity  oils  can  be  used  and  yet 
they  will  be  found  to  be  more  "oily"  than  the  more  viscous 
straight  mineral  oils;  therefore  they  reduce  friction  and  last 
longer.  They  seem  to  form  a  very  tenacious  oil  film  in  the 
spindle  bearings  and  are  displaced  only  with  difficulty.  This  is 
no  doubt  due  to  the  presence  of  the  fixed  oil  which  we  know  excels 
over  mineral  oil  in  the  property  of  oiliness. 

The  best  practice  is  to  oil  the  neck  bearings  of  flyer  spindles 
and  mule  spindles  while  the  frames  are  running.  This  is  Conti- 
nental practice  and  means  that  thinner  oils  can  be  used  efficiently, 
as  one  is  always  certain  of  the  necks  being  thoroughly  oiled. 
Oiling  when  the  spindles  are  standing,  as  is  the  practice  in  Eng- 
land, may  mean  that  in  some  necks,  particularly  when  they  are 
worn,  the  oil  runs  straight  through  the  clearance  between  neck 
and  collar.  When  neck  bearings  are  fitted  with  felt  pads  for 
lubrication,  it  is  immaterial  whether  they  are  oiled  while  the 
spindles  are  running  or  when  standing. 

As  to  typical  savings  in  power  accomplished  on  spinning 
frames,  see  pages  315  to  319.  In  most  mills  the  oils  recommended 
above  will  save  over  8  per  cent,  of  the  departmental  loads, 
equivalent  to  6  per  cent,  of  the  full  mill  load. 

Top  Rollers. — In  some  cotton  mills  Spindle  Oil.  No  3  is  often 
sufficiently  viscous  for  the  top  rollers,  but  in  others,  as  well  as 
in  most  other  spinning  mills,  woollen  and  worsted  mills  in  par- 
ticular, a  more  viscous  oil  is  required;  and  speaking  generally,  the 
engine  oil  used  in  the  power  house  will  prove  very  suitable  as  a 
top  roller  oil.  In  flax  mills  a  special  preparing  room  oil  is  often 
used  for  the  preparing  room  and  for  the  press  rollers  in  particular. 
This  is  found  necessary  when  the  roller  covers  are  not  fitted  with 
flannels;  but  if  they  are  so  fitted,  an  oil  like  Bearing  Oil  No.  3 
can  be  used  satisfactorily.  Tallow  or  white  tallow  greases  are 
often  used  for  top  rollers,  especially  when  they  are  badly  worn 
and  therefore  difficult  to  lubricate;  bad  lubrication  of  the  top 
rollers  causes  a  jerky  motion  and  unevenness  in  the  yarn. 

Traveller. — The  ring  upon  which  the  traveller  moves  in  a  ring 
spinning  frame  should  be  sparingly  greased  with  clean  tallow. 

Combers. — For  combers  a  viscous  oil  like  the  engine  oil  used 
in  the  engine  room  must  be  used  for  lubrication  of  the  slow  mov- 
ing parts,  whereas  the  spindle  oil  should  preferably  be  used  for 
the  dabbing  motions.  When  the  circles  are  highly  steam  heated, 
anon-carbonizing,  very  viscous  mineral  oil  is  required,  having  a 
Saybolt  viscosity  of  say  75"  at  212°F.  and  made  from  a  pale,  non- 
paraffinic  base,  distilled  oil  mixed  with  good  quality  filtered  cylin- 
der stock. 


TEXTILE  MACHINERY  315 

Weaving  Mills.— Loom  oils  should  preferably  be  compounded 
for  the  same  reasons  as  given  for  spindle  oils. 

The  percentage  of  compound  need  not  be  more  than  6  per  cent, 
unless  particular  stainless  properties  are  required.  For  high 
speed  light  looms,  Loom  Oil  No.  2  or  3  is  recommended  and  for 
slow  speed  heavy  looms,  Loom  Oil  No.  4.  The  oils  must  of  course 
be  sold  as  loom  oils;  if  branded  spindle  oils  they  would  almost 
certainly  be  condemned  by  the  mill  people.  As  stainless  loom 
oils  or  as  stainless  picker  spindle  oils  (particularly  when  over- 
pick  motion  is  employed)  Loom  oils  No.  2S,  3S  and  4S  are 
recommended. 

Bleaching,  Dyeing,  Printing  and  Finishing. — Bearing  Oils  Nos. 
3  and  4  are  generally  used.  The  calenders,  however,  require  a 
very  viscous  oil,  such  as  Bearing  Oil  No.  5  or  oil  even  more  viscous. 

High  melting  point  greases,  with  melting  points  suitable  for 
the  temperature  of  the  bearing  journals,  are  also  used. 

HOSIERY  MACHINES,  POWER  SEWING  MACHINES,  ETC, 

Hosiery  machines  are  chiefly  knitting  machines,  and  either 
straight  bar  machines,  knitting  flat  pieces  of  material,  or  circular 
machines,  knitting  tubular  pieces.  Bar  machines  have  several 
hundreds  of  needles  and  the  largest  circular  machines  many 
thousands  of  needles.  The  needles  require  some  slight  lubrica- 
tion so  that  the  yarn  may  pass  easily  through  them.  The  lubri- 
cation is  done  by  the  yarn,  which  before  entering  the  .machines  is 
passed  through  a  trough  containing  emulsified  lather  oil;  as  the 
yarn  leaves  the  trough,  surplus  lather  is  squeezed  out  by  rollers. 

For  general  lubrication  of  most  circular  machines  and  power 
sewing  machines  Loom  Oil  No.  2S  will  be  found  suitable.  Bar 
machines  require  a  somewhat  heavier  oil,  such  as  Loom  Oil  No.  3S 
and  this  oil  may  also  be  recommended  for  circular  machines 
which  have  become  worn. 

Stainless  properties  are  practically  always  required,  arid  the 
oil  ought  to  be  thoroughly  tested  in  this  respect  as  mentioned, 
page  310. 

POWER  REDUCTION  IN  TEXTILE  MILLS 

Very  great  reductions  in  power  can  be  accomplished  by  paying 
careful  attention  to  the  selection  of  suitable  oils  for  each  depart- 
ment in  the  mill,  as  well  as  for  the  mill  shafting  and  the  power 
house. 

In  a  ring  spindle  frame,  for  example,  about  80  per  cent,  of  the 
power  is  required  for  driving  t.bc  fnimc  empty,  only  20  per  cent. 


316  PRACTICE  OF  LUBRICATION 

being  consumed  in  handling  the  yarn.  In  the  case  of  prepar- 
ing machinery  an  even  greater  percentage  of  the  full  load 
power  is  required  to  run  the  machines  or  frames  empty. 

In  a  jute  spinning  frame  of  the  ordinary  type  the  power  con- 
sumed usefully  is  very  much  the  same  as  in  a  ring  spindle  frame, 
but  in  the  modern  spinning  frames,  in  which  the  tension  of  the 
driving  bands  is  kept  uniform,  there  is  a  great  reduction  in  the 
power  consumed  by  the  frame,  and  only  65  per  cent,  of  the  full 
load  power  is  required  for  running  empty. 

In  mules  or  looms  a  great  portion  of  the  power  is  used  in  over- 
coming the  inertia  of  the  moving  parts  which  have  to  be  acceler- 
ated, stopped,  and,  in  the  case  of  the  loom,  quickly  changed.  In 
the  loom,  for  example,  the  sley  moves  backward  and  forward 
quickly,  the  picker  motion  just  as  quickly,  and  the  shuttle  is 
thrown  quickly  to  and  fro,  all  of  which  requires  a  geat  deal  of 
power,  so  that  the  percentage  of  power  influenced  by  lubrication 
in  a  mule  or  loom  is  less  than  in  ring  spinning  frames. 

In  the  average  steam-engine  driven  textile  spinning  mill,  1% 
to  2  Ib.  of  coal  are  consumed  per  indicated  horsepower  per 
hour,  and  the  heat  value  actually  converted  into  useful  work  in 
the  form  of  preparing  or  spinning  the  yarn,  etc.,  will  not  be  more 
than  1J/2  Per  cent,  to  2  per  cent,  of  the  heat  value  of  the  coal  used 
under  the  boilers. 

The  possible  saving  in  power  by  introducing  correct  grades  of 
spindle  and  loom  oils  is  nearly  always  considerable.  To  take  an 
example:  On  a  ring  spinning  frarre  using  an  oil  having  a  Say- 
bolt  viscosity  of  95"  at  104°F.,  another  oil  with  a  Saybolt 
viscosity  of  55 "  at  104°F.  was  introduced;  both  were  straight 
mineral  oils.  The  results  were  as  in  table  on  p.  317: 

The  saving  in  power  in  this  case  amounted  to  8.8  per  cent, 
and  indicates  the  results  which  can  be  obtained  in  most  textile 
mills,  as  the  first  oil  used  is  typical  of  the  ring  spindle  oils  now 
in  general  use  and  is  quite  unnecessarily  viscous,  except  perhaps 
for  frames  with  old  and  worn  Rabbeth  spindles.  Whenever  a 
change  from  a  viscous  oil  to  one  less  viscous  is  carried  out,  the 
low  viscosity  oil  will  turn  black,  the  discoloration  being  due  to 
extremely  fine  metallic  particles  from  the  rubbing  surface.  In 
other  words,  very  slight  wear  takes  place,  the  surfaces  adapting 
themselves  to  the  new  oil.  After  the  pumping  out  and  recharg- 
ing process,  the  fresh  oil  should  work  perfectly  clean. 

Such  a  saving  in  power  is  worth  many  times  the  value  of  the 
oil  itself,  and  in  addition  the  yarn  produced  by  the  frame  will 
be  found  more  uniform,  due  to  the  smoother  running  of  the 
spindles. 


TEXTILE  MACHINERY 
PARTICULARS  OF  RING  FRAME 


317 


Number  of  spindles 300 

Diameter  line  shaft  pulley 40  inches. 

Diameter  frame  pulley 15  inches. 

Diameter  tin  roller 10  inches 

Diameter  whorl 1  inch. 

Viscous        !  Low  viscosity 
oil  oil 

(1)  Influencing  Conditions. 

Counts  spun 10)£  10>i 

Weight  of  yard  per  doff \  14.6  Ihs.  14.6  Ih. 

Room  temperature !  89°F.  90°F. 

Relative  humidity j  62%  62% 

(2)  Power  (measured  by  Emersons  Dynamometer),  \ 

Brakehorse  power !     3  . 64  3 . 32 

(3)  Temperatures. 

Temperature  of  spindle  rail j     98°F.  97°F. 

Frictional  heat I       9°F.  7°F. 

(4)  Loss  due  to  Belt  and  Band  Slip. 

Speed  of  line  shaft,  r.p.m 281  281 

Theoretical  speed  of  tin  roller |     749  749 

Registered  speed  of  tin  roller ;     740  745 

Belt  Slip j       1.2%  0.7% 

Theoretical  speed  of  spindles j  7400  7450 

Registered  speed  of  spindles 7010  7085 

Driving  band  slip j       5.3%  4.9% 


Improved  lubrication  means  lower  frictional  heat,  which  is 
evidenced  by  a  lower  rise  in  temperature  of  the  spindle  rail 
above  the  room  temperature. 

The  driving  bands  which  run  over  the  tin  roller  and  drive  the 
spindle  always  slip  slightly;  when  they  are  in  proper  condition 
the  slip  should  not  be  more  than'  a  few  per  cent.  The  lower 
friction  of  the  spindles  will  reduce  the  band  slip  and  thus  slightly 
increase  the  spindle  speed,  as  shown  by  the  test.  Less  band  slip 
also  means  less  wear  of  the  driving  bands  and  the  annual  con- 
sumption of  driving  bands  is  quite  a  good  indication  of  the  quality 
of  ring  spindle  oil  used.  The  reduced  power  consumption  of  the 
frame  will  tend  to  decrease  the  belt  'slip  in  the  driving  belt,  and 
this  effect  is  also  shown  in  the  test  figures. 

In  a  worsted  spinning  mill  a  test  was  carried  out  on  a  spinning 
frame  having  216  open  type  flyer  spindles.  The  oils  in  use  on  the 
two  tests  were  Oil  No.  1  and  Oil  No.  2.  Oil  No.  1  was  a  straight 
mineral  oil  having  a  Saybolt  viscosity  of  165"  at  104°F.  Oil 
No.  2  is  spindle  oil  No.  2  specified  on  page  311.  The  power 
measurements  were  recorded  by  an  Emerson  Dynamometer, 


318 


PRACTICE  OF  LUBRICATION 


and  besides  particulars  of  the  horsepower  readings  were  obtained 
of  the  rail  temperature,  room  temperature,  relative  humidity, 
tin  roller  speeds  and  spindle  speeds,  every  10  minutes  for  two 
hours  in  the  forenoon  and  two  hours  in  the  afternoon.  Before 
testing,  the  frame  was  cleaned  and  well  oiled  with  Oil  No.  1  and 
after  the  first  test  was  completed  the  footsteps  were  again  wiped 
out  and  Oil  No.  2  was  put  into  use.  The  frame  was  then  allowed 
to  run  for  a  full  day  before  the  second  test  took  place. 


Oil  in  use 


H.P.  required    j         Rise  in 
to  drive         j    temperature 
frame  of  spindle  rail 


Oil 

No 

1                                                               .,.•». 

2 

39 

.  i 
10 

3 

Oil 

No. 

2  :  

2 

15 

,5 

4 

Reduction  in  H.P.  required  to  drive  frame. .  .0.24  or  10.0  per  cent. 
Reduction  in  temperature  of  spindle  frame.  .  .  .4.9°F.  or  47.6  per  cent. 


Tin  roller  speeds  per  minute 


Spindle  speeds  per  minute 


Cal- 
culated 

Actual 

Per  cent, 
slip 

Cal- 
culated 

i      Actual 

Per  cent, 
slip 

j 

: 

With 

Oil 

No. 

1 

231 

225 

3.         2.47 

2,054 

1 

,893 

7.8 

With 

Oil 

No. 

2  j       231 

225 

4    ]      2.42 

2,054 

4 

,900         7.5 

The  temperature  of  the  atmosphere  and  the  relative  humidity 
were  the  same  on  both  tests. 

In  one  mill  the  introduction  of  Spindle  Oil  No.  2  for  cap  spindles 
reduced  the  wear  .of  the  driving  bands  very  considerably.  It 
was  brought  to  the  Overlooker's  notice  that  the  band  boy  had 
very  little  work  to  do,  and  when  asked  why  he  did  not  attend 
to  the  bands  he  replied  that  as  soon  as  the  new  oil  was  put  into 
use  the  bands  very  seldom  broke  and  he  had  none  to  repair. 

In  another  case  the  power  consumption  of  the  frames  with 
oil  No.  1  was  so  great  that  the  belts  were  always  slipping  on  the 
pulleys.  It  was  not  possible'  to  get  all  the  spinning  frames  run- 
ning until  7  o'clock,  as  it  took  some  considerable  time  before 
the  oil  became  warm  and  fluid  enough  to  reduce  the  power  con- 
sumption of  the  frames.  The  steam  engine  driving  the  mill  was 
hardly  powerful  enough  to  cope  with  the  load. 

Comparative  power  tests  in  textile  mills  should  therefore 
never  be  carried  out  on  Mondays  when  the  mills  have  been  shut 
down  for  the  week-end.  The  oil  cools  down  in  the  bearings  and 


TEXTILE  MACHINERY  319 

the  starting  load  on  the  Monday  morning  is  always  considerably 
higher  than  later  on  during  the  week. 

When  engines  are  overloaded,  it  is  often  difficult  to  start  the 
mill  on  full  load,  on  Monday  mornings  in  particular,  and  it  may 
even  be  necessary  to  leave  out  one  or  two  departments  until  the 
engine  eventually  is  able  to  cope  with  the  load.  The  introduction 
of  more  suitable  grades  of  oil  reduces  the  horsepower  required 
and  particularly  the  starting  horsepower  in  the  early  part  of 
the  week,  so  that  the  engines  are  able  to  get  up  their  normal  speed 
much  more  rapidly  and  maintain  their  speed  more  uniformly 
during  the  day.  There  have  been  many  cases  of  overloaded 
engines  which  after  a  change  in  lubrication  have  been  found  quite 
powerful  enough  to  drive  the  mills,  so  that  a  study  of  the  lubri- 
cating conditions  has  saved  such  mills  the  heavy  expense  of  put- 
ting in  a  new  engine  or  introducing  electric  motors  to  take  care 
of  part  of  the  load.  When  better  lubricants  are  introduced  the 
improved  working  of  the  machines  is  soon  observed  by  the  easier 
starting  of  the  machines  or  by  their  running  for  a  longer  time 
after  the  driving  belt  has  been  moved  on  to  the  loose  pulley. 

Quite  a  simple  test  for  the  engine  and  shafting  load  is  to  run 
the  engine  and  shafting  at  the  dinner  hour  when  all  the  machinery 
in  the  mill  is  stopped;  then  shut  off  steam  and  observe  the 
number  of  revolutions  made  by  the  engine  before  it  comes  to  a 
standstill,  and  the  time  taken.  An  improvement  in  lubrication 
is  immediately  shown  by  the  greater  number  of  revolutions  and 
the  longer  time  that  passes  before  the  engine  comes  to  rest. 

When  an  appreciable  reduction  in  .power  has  been  accom- 
plished in  a  textile  mill  by  introduction  of  better  lubricants,  the 
main  effects  are  the  following: 

(1)  A  reduction  in  the  total  horsepower  of  the  mill  as  well  as  in  the  engine 
and  shafting  load  and  the  power  consumed  by  each  department  in  the  mill. 

(2)  A  reduction  in  the  amount  of  coal  required  for  power  purposes.     When 
the  reduction  in  power  is  appreciable  it  should  always  be  possible  to  find  a 
corresponding  reduction  in  the  coal  consumption,  particularly  when  the 
amount  of  coal  used  for  heating  and  power  are  kept  separate. 

(3)  A  reduction  in  the  temperature  of  all  bearings  and  spindle  bases. 

(4)  An  increase  in  the  speed  of  countershafting,  -machines  and  spindles 
due  to  reduced  slipping  of  driving  belts  and  driving  bands.     If  the  engine  has 
been  overloaded  the  reduction  in  power  will  bring  about  an  increase  in  the 
engine  speed  and  the  engine  will  reach  its  normal  speed  more  quickly  after 
starting. 

(5)  A  slight  increase  in  production,  chiefly  due  to  fewer  stoppages,  as  many 
stoppages  are  caused  through  defective  lubrication. 

(6)  There  will  be  a  decrease  in  the  wear  and  tear  of  the  machines  as  well 
as  of  belts  and  driving  bands.     The  decrease  in  the  wear  of  the  driving  bands 
may  often  be  quite  considerable. 


CHAPTER  XXIII 
MINE  CAR  LUBRICATION 

The  tubs  in  collieries  are  known  by  many  names,  such  as  trains, 
hutches  (Scotland),  mine  cars  (U.  S.  A),  etc.  The  following  re- 
marks chiefly  apply  to  mine  cars  in  collieries. 

Their  lubrication  consumes  on  an  average  50  per  cent,  of  the 
oil  used  in  a  colliery  and  is  of  great  importance,  as  trouble  with 
the  tub  lubrication  may  easily  cause  reduced  output.  The  tubs 
are  preferably  made  of  steel;  with  wooden  tubs  dust  shakes 
through  the  floors,  contaminates  the  axles,  and  interferes  with 
lubrication.  Their  carrying  capacity  is  from  4  cwt.  to  2  tons. 
Tubs  have  two  axles  usually  of  rolled  steel  ranging  in  diameter 
from  \Y±  inches  to  2  inches,  wheels  ranging  from  7  inches  to  16 
inches  in  diameter,  and  bearings  of  a  length  preferably  not  less 
than  twice  the  diameter  of  the  axle. 


FIG.   138.— Open  type  bearing. 

Wheels  and  Axles. — With  fast  wheels  the  wheels  are  riveted  to 
the  axle  which  revolves  in  the  cod  bearings. 

With  loose  wheels  both  wheels  are  loose  on  the  axle,  which  does 
not  revolve. 

With  loose  wheels  and  axles  the  wheels  as  well  as  the  axles,  are 
free  to  rotate.  Where  the  track  has  many  curves  this  system,  or 
a  combination  of  one  fast  and  one  loose  wheel  is  often  used. 

Cod  Bearings. — These  may  be  either  outside  or  inside  bearings 
and  either  open  or  enclosed.  Fig.  138  shows  a  typical  open 
type  bearing.  The  spectacle  plate  (1)  should  be  bent  well  to  one 
side,  so  that  it  does  not  foul  the  automatic  oilers,  when  the  tub 
passes  over  them.  The  bolts  (2)  should  preferably  be  put  in 
from  the  bottom  and  must  not  project  below  the  axle,  as  in  Fig. 
139  when  they  will  foul  the  oilers.  Fig.  140  also  shows  an  un- 
desirable condition  from  the  oiling  point  of  view,  -and  it  may  be 
produced  by  excessive  wear  of  the  bearing  shown  in  Fig.  138. 

320 


MINE  CAR  LUBRICATION 


321 


Cod  bearings  may  be  of  cast  iron  but  are  usually  of  cast  steel, 
and  where  there  is  no  dust  or  the  dust  is  not  of  a  gritty  nature  they 
are  preferably  lined  with  white  metal.  The  question  of  grit  is 
of  importance  only  when  the  speed  of  the  tubs  is  sufficiently  great 
to  raise  the  dust  to  any  extent. 


•If 


1  , 


FIG.   139. 


FIG.   140. 


Cod  bearings. 


When,  as  is  sometimes  the  case,  the  bearing  entirely  encloses 
the  axle,  or  the  spectacle  plate  is  in  the  centre,  the  axles  cannot  be 
oiled  automatically,  except  by  squirt  oilers,  as  for  example  the 
Abbott  oiler  which  will  be  referred  to  later.  Fig.  141  illus- 
trates the  Rowbotham  wheel,  much  used  in  South  Wales  on 
account  of  the  fine  dust  existing  in  the  mines.  The  wheel  is 


FIG.   141. — Rowbotham  wheel. 

loose  on  the  axle  and  the  hub  serves  as  an  oil  reservoir;  the  oil  is 
injected  by  a  syringe  against  a  self-closing  ball  valve,  as  shown. 
Enclosed  wheels  of  similar  types  are  much  used  in  the  United 
States  frequently  employing  oil  soaked  waste,  and  on  the  Con- 
tinent there  are  several  types  of  roller  or  plain  bearings  so  arranged 
that  the  bear-ing  housings  at  either  end  of  the  axle  are  combined 
and  form  a  sleeve  surrounding  the  axle,  as  shown  in  Fig.  142. 
The  space  between  the  axle  and  the  sleeve  is  filled  with  oil  through 
21 


322 


PRACTICE  OF  LUBRICATION 


a  filling  hole  in  the  centre.  The  lubrication  is  very  economical; 
one  filling  may  last  a  month  or  more.  The  oil  works  its  way 
out  through  the  ends  and  keeps  the  bearings  clean.  The  bearings 
should  have  good  felt  packings  when  using  oil,  as  otherwise  it 
works  out  too  freely  and  is  wasted.  With  roller  bearings  a  very 
soft  grease  is  better  than  oil  and  more  economical. 

OILERS  AND  GREASES 

Hand  Oiling. — The  tubs  are  still  in  some  mines  oiled  by  hand, 
although  this  practice  is  fast  disappearing.  The  tubs  are  turned 
over  first  on  one  side  then  on  the  other;  the  oil  is  applied  through 
" coffee  pots";  loose  wheels  are  given  a  "spin"  when  being  oiled 
to  get  the  oil  well  worked  into  the  bearing.  By  flattening  the  end 
of  the  oil  can  spout  it  is  possible  to  reduce  the  waste  of  oil  to 


FIG.   142. — Roller  bearings  for  mine  cars. 

some  extent.  It  is  good  practice  to  use  thick  oil  and  heat  it  in  a 
steam  heated  tank;  cold  oil  will  not  run  through  a  flattened  spout, 
and  if  an  ordinary  wide  spout  is  used  most  of  the  oil  will  be  wasted. 

With  fast  wheels,  the  axles  may  be  .oiled  by  hand  by  means  of 
a  brush;  to  avoid  undue  waste,  the  brush  should  not  be  dipped 
in  the  oil,  but  into  cotton  or  wool  waste  kept  well  soaked  with  oil. 

Hand  greasing  may  be  done  by  a  stick  or  a  brush  but  is  always 
very  wasteful;  the  surplus  grease  drops  on  to  the  track  and  makes 
it  greasy  and  dirty. 

Mechanical  Oilers. — Fig.  143  shows  an  early  type  of  greaser, 
a  scalloped  wheel  connected  to  the  axle  by  a  spiral  spring,  which 
allows  the  wheel  to  be  depressed  when  the  axle  passes  over  it  and 
gets  smeared  with  grease.  Coal  dust  gets  into  the  trough  and 
gives  trouble.  When  the  grease  is  thick  or  becomes  thick,  due 


MINE  CAR  LUBRICATION 


323 


to  cold,  the  wheel  cuts  a  track  in  it  and  revolves  without  lifting 
the  grease.  Revolving  brushes  have  been  used  instead  of  the 
wheel  but  are  very  wasteful  indeed. 

The  "knock  out"  greaser,  Fig.  144,  is  a  better  form  of  greaser; 
it  is  simple  and  accessible;  the  wheel  can  be  lifted  right  out.  This 
greaser  is  also  used  for  oil  but  should  then  have  a  brake  fitted  so 


FIG.  '143. — Scalloped  wheel  greaser.         FIG.   144. — "Knock  out"  greaser. 

that  it  soon  stops  after  the  axles  have  passed,  otherwise  it  causes 
waste  by  throwing  the  oil. 

The  disadvantage  of  this  and  similar  greasers  when  using  oil 
is  that  the  oil  drains  off  during  an  interval,  so  that  when  the  next 
set  of  tubs  comes  over,  the  first  few  tubs  do  not  get  properly  oiled. 


FIG.   145. — Automatic  pump  oiler.    (Woodman  &  Thomsen,) 

All  tub  oilers  should  be  so  designed  that  none  of  the  axles  can  pass 
over  without  being  oiled.  Most  types  have  some  form  of  pump 
actuated  by  the  tub  axles;  the  wheels  of  the  tubs  passing  over  an 
oiler  should  therefore  be  of  the  same  size  and  as  uniform  as  pos- 
sible. When  the  wheels  are  much  worn  the  axles  of  those  par- 
ticular tubs  are  nearer  the  ground,  depress  the  pump  plunger 
too  much,  and  cause  waste  of  oil. 


324  PRACTICE  OF  LUBRICATION 

The  oiler  or  its  foundation  should  be  secured  firmly  to  the  rails ; 
otherwise  it  may  be  pushed  into  the  ground  with  the  result  that 
the  axles  no  longer  depress  the  plungers  sufficiently. 

Fig.  145  illustrates  an  oiler  designed  by  W.  A..  E.  Woodman 
and  the  author.  It  is  suitable  only  for  open  type  bearings  (Fig. 
138)  and  fast  wheels.  It  has  a  large  container;  the  lid  carries 
the  pump  barrel  with  its  suction  valve.  The  bow  is  guided  by 
two  vertical  guide  bars  and  carries  the  pump  plunger  with  a  de- 
livery valve  at  the  bottom.  The  guide  bars  are  connected  by  a 
cross  piece,  which  is  forced  upward  by  a  spring  against  a  stop; 
the  stop  is  adjusted  vertically  by  a  single  outside  adjustment, 
thus  determining  the  depression  of  the  plunger  when  the  axles 
pass  over  the  bow,  and  wipes  the  oil  from  the  oil  delivery  well  in 
the  centre  of  the  bow.  The  lid  entirely  covers  the  container 
and  is  provided  with  a  large  filling  hole ;  the  edges  of  the  hole  are 
raised  a'bove  the  level  of  the  lid,  to  prevent  dust  and  dirt  getting 
in  when  the  container  is  being  filled.  This  is  a  very  important 
point,  and  for  the  same  reason  the  filling  lid  is  so  designed  that 
it  cannot  be  left  open,  but  automatically  falls  and  closes  the 
opening. 

In  many  types  of  oilers  for  open  type  bearings,  the  haulage 
ropes  and  coupling  chains  are  liable  to  get  underneath  the  bow  and 
bodily  pull  the  oiler  out  of  the  track.  This  has  been  provided 
against  by  placing  at  either  end  of  the  bow  a  fin,  which  is  cast  on 
to  the  lid  and  gives  an  inclined  plane  for  the  rope  or  chain  to  run 
up  and  slide  clear  over  the  bow.  These  fins  also  act  as  buffers 
against  severe  end  shocks. 

The  oiler  has  to  be  well  made,  but  in  the  author's  experience 
tub  oilers  cannot  be  too  well  made.  The  oiler  shown  has 
worked  under  very  severe  conditions  in  South  Wales  (very 
heavy  tubs)  where  no  other  oiler  has  been  able  to  stand  up 
to  the  conditions.  After  many  months'  working  no  perceptible 
wear  had  taken  place,  no  dirt  had  got  into  the  container 
(only  a  coarse  sieve  is  provided),  and  the  adjustments  had 
never  been  touched.  Equally  good  results  have  been  obtained 
in  Lancashire  and  other  collieries,  where  the  conditions  are  much 
less  severe. 

The  oilers  are  usually  placed  on  the  same  foundation,  but 
sometimes  it  is  best  to  " stagger"  them.  This  gives  more  room 
for  the  ponies  (where  ponies  are  used)  and  is  also  advantageous 
where  the  spectacle  plates  are  inclined  to  foul  the  oilers.  The 
rail  at  the  first  of  a  pair  of  oilers  and  a  little  before  is  raised  say 
1J/2  inches  above  the  other  rail.  This  makes  the  tub  body  slide 
over  toward  the  lower  rail  and  gives  more  clearance  to  oil  the 


MINE  CAR  LUBRICATION 


325 


underside  of  the  axle  in  the  cod  bearing.  The  same  performance 
is  reversed  at  the  next  oiler  which  is  placed,  say,  10  to  15  yards 
farther  along  the  track. 

On  the  surface  the  oilers  should  not  be  exposed  to  rain,  but 
placed  under  a  roof  or  shelter.  Down  pit  the  oilers  should  be 
laid  down  in  a  dry  place  and  not  where  surface  or  roof  water  is 
likely  to  come  in  contact  with  them.  On  entering  a  wet  district 
the  tubs  should  be  oiled  so  that  the  oil  film  will  last  until  the  tubs 


OC\\\\N 

FIG.   146.— Abbott  Boiler. 

reach  the  next  oiler,  which  should  be  placed  immediately  after 
the  wet  district.  It  is  much  easier  to  renew  and  maintain  the 
oil  film  if  it  is  never  allowed  to  be  completely  washed  away;  the 
oil  does  not  adhere  well  to  a  wet  axle. 

Fig.  146  shows  one  form  of  the  Abbott  oiler  oiling  outside 
axle  bearings  of  the  type  shown  in  Fig.  140,  which  can  obviously 
not  be  oiled  by  the  oiler  shown  in  Fig.  145.  The  plungers  (1) 
are  depressed  quickly  and  so  timed  that  they  squirt  oil  on  to  the 
underside  of  the  axles;  surplus  oil  is  caught  by  the  saveall  (2). 


326  PRACTICE  OF  LUBRICATION 

The  oil  in  Abbott  oilers  must  be  steam  heated  to  give  a  good 
and  uniform  squirt;  for  this  reason  they  cannot  be  used  down  pit, 
where  there  is  no  steam. 

Distance  Between  Oilings. — Apart  from  wet  districts  it  may  be 
said  that  the  larger  the  wheels  and  the  cooler  the  pit,  the  longer 
distances  can  be  allowed  between  the  oilers,  other  things  being- 
equal.  The  axles  should  never  be  allowed  to  run  dry;  it  is  better 
to  space  the  oilers  closer  together  and  give  them  less  oil  per  oiler, 
than  to  space  the  oilers  so  far  apart  that  there  is  a  risk  of  under- 
lubricating  the  axles.  Efficient  oiling,  saves  wear  and  tear  and 
means  less  power  required  for  hauling  the  tubs.  It  is  good  prac- 
tice not  to  exceed  1^  miles  between  oilings,  and  with  small 
wheels  and  narrow  bearings  oiling  every  mile  will  be  required. 

In  some  mines,  using  a  very  viscous  oil,  tubs  have  run  as 
much  as  four  miles  on  one  oiling,  but  the  lubrication  has  not  been 
all  that  could  be  desired. 

Before  grades  of  tub  oils  and  greases  are  described,  it  is 
necessary  to  refer  to  the  various  systems  of  haulage. 

SYSTEMS  OF  HAULAGE 

With  endless  rope  haulage  the  empty  tubs  are  continuously 
and  slowly  hauled  into  the  mine,  and  return  loaded,  the  speed  of 
haulage  being  from  2  to  4  miles  per  hour. 

With  main  haulage  the  shaft  is  inclined  toward  the  workings, 
the  incline  exceeding  1  :  24.  The  empty  tubs  run  into  the  shaft 
by  gravity  and  are  hauled  out  loaded;  only  one  rope  and  one 
haulage  drum  are  employed. 

With  main  and  tail  haulage  two  ropes  are.used;  the  main  rope 
hauls  the  loaded  tubs  out  and  the  tail  rope  pulls  the  empty  tubs 
in.  The  haulage  drums  are  both  operated  by  the  same  engine. 
The  speed  for  main  and  tail  haulage  may  be  as  high  as  20  miles 
per  hour. 

The  haulage  ropes  are  driven  either  by  a  steam  haulage  engine 
or  by  an  electric  haulage  engine.  In  the  United  States  ropes 
are  discarded  in  many  mines  and  the  mine  cars  pulled  out  or  in 
by  electric  or  compressed  air  locomotives. 

LUBRICANTS 

Grease  can  be  used  only  for  slow  speed  conditions;  if  used  on 
main  and  tail  haulage  it  gives  a  great  deal  of  trouble  and  wastes 
much  power  in  hauling  the  tubs;  also  the  wear  is  very  excessive. 
Good  tub  oil  as  compared  with  grease  gives  cleaner  and  bettor 


MINE  CAR  LUBRICATION  327 

lubrication  and  not  only  does  it  save  a  great  deal  of  power,  but 
rightly  applied  it  also  saves  in  cost.  In  most  cases  where  a 
change  has  been  made  from  grease  to  oil,  the  saving  in  consump- 
tion is  50  per  cent,  or  over.  With  electrically  operated  haulage 
the  difference  between  grease  and  oil  or  even  different  qualities 
of  oil  is  readily  observed. 

With  ball  or  roller  bearings  there  is  very  little  difference  in 
friction  between  oil  and  grease.  Very  little  lubricant  is  required 
but  it  must  be  of  good  quality  (see  under  Ball  and  Roller  Bearings). 

The  lubricant  must  be  selected  according  to  the  temperature 
of  the  mine,  whether  it  is  dry  or  wet,  the  amount  and  nature  of 
the  dust,  the  type  of  oiler  employed,  and  the  distances  between 
oilings. 

Temperature. — In  deep,  badly  ventilated  pits  the  temperature 
is  higher  than  in  shallow  well  ventilated  pits.  The  higher  the 
temperature  the  more  viscous  the  oils  required.  In  cold  pits 
a  good  cold  test  will  be  required,  so  that  the  oil  will  not  be  too 
sluggish  in  the  automatic  oilers. 

Wet  Pits. — In  very  wet  pits  good  quality  grease  may  have  to  be 
used,  if  the  tubs  must  run  long  distances  between  oilings.  It 
is  not  so  easily  washed  off  the  axles  as  is  oil.  Tub  oils  for  wet 
pits  should  have  a  tendency  to  emulsify  with  water. 

Dust. — Fire  clay  dust  and  coal  dust  have  a  drying  effect  on  the 
oil  film.  Free  flowing  oils  and  frequent  oilings  are  desirable  with 
these  kinds  of  dust. 

Stone  or  flint  dust  will  cause  heavy  wear;  the  wear  can  be 
minimized  only  by  using  viscous  oils  of  good  quality  and  by 
frequent  oilings.  If  a  sticky  oil  is  used,  the  dust  forms  a  grinding 
paste  with  the  oil  and  causes  heavy  friction  and  wear. 

Type  of  Oiler. — Wheel  greasers  (Figs.  143  and  144)  can  use 
oil  of  almost  any  description,  and  also  grease  as  long  as  it  is  not 
too  thick. 

Abbott  oilers  can  use  oils  with  a  poor  cold  test,  as  they  are 
usually  steam  heated.  Such  oils  solidify  on  the  cold  axles  and 
form  a  film  with  good  lasting  properties  if  the  oil  is  of  good 
quality. 

Pump  oilers  like  Figs.  145  and  146  when  not  steam  heated 
cannot  use  oils  which  are  so  sluggish  at  the  working  temperature 
that  the  pump  fails  to  act. 

Hand  Oiling. — When  the  oil  is  heated  it  need  not  have  a  good 
cold  test,  but  this  may  be  necessary  when  it  is  not  heated. 

Distance  Between  Oilings.— With  long  distances  between  oil- 
ing more  viscous  oils  are  required  than  when  the  oilers  are  closer 
together. 


328  PRACTICE  OF  LUBRICATION 

GRADES  OF  OILS  AND  GREASES 

It  is  customary  to  use  black  oils,  one  for  summer  use  with  a 
cold  test  of  25°F.  to  30°F.  and  a  winter  oil  with  a  cold  test  of  5°F. 
to  15°F..  These  oils  are  dark  residual  oils  from  distilling  lubri- 
cating crudes,  or  from  redistillation  of  lubricating  oil  distillates, 
or  they  are  mixtures  of  such  oils  with  low  viscosity,  low  cold  test 
oils,  so  as  to  produce  oils  of  the  right  viscosity  and  cold  test. 

The  asphalt  contents  should  preferably  not  exceed  3  per  cent, 
in  the  better  quality  oils,  but  for  rough  service,  oils  with  much 
higher  asphalt  contents  have  been  used.  Typical  viscosity 
figures  for  black  oils  are  given  in  Table  No.  13. 

TABLE  No.  13 

Saybolt  viscosity,  in  sees. 

Cold  test, 

in°F 
104°F.  140°F. 


1 

1 

Winter  black  oil 

1  ' 
500 

200 

. 
Mb 

Summer  black  oil  

600 

280 

2%o 

Heavy  black  oil            .  .        

1200 

380 

5  Ho 

Black  Tub  Greases  are  usually  rosin  greases.  Sometimes  so 
called  Floating  Greases,  containing  talc,  are  used. 

There  are  various  formulae  and  the  better  qualities  contain  no 
filler.  A  rough  test  for  the  presence  of  filling  material  is  to  burn 
a  sample  and  examine  the  residue  (lime,  talc,  etc.) 


CHAPTER  XXIV 

STEAM  ENGINES 

LUBRICATION  OF  CYLINDERS  AND  VALVES 
Stationary  and  Marine  Engines. 

With  special  chapters  on: 

Corliss  Valve  Engines. 
Colliery  Winding  Engines. 
Uniflow  Engines  (Stumpf  Engines). 
Marine  Engines. 
Locomotives. 

STEAM  ENGINES,  STATIONARY  AND  MARINE 

Steam  engines  are  the  most  reliable  and  most  highly  developed 
and  specialized  of  all  power  producers. 

Most  land  steam  engines  are  horizontal  and  practically  all 
marine  engines  are  vertical,  except  a  few  " inclined"  engines 
employed  in  paddle-steamers! 

They  can  be  classified  according  to : 

1.  Arrangement  and  number  of  cylinders. 

2.  Type  of  valves  employed. 

1.  Arrangement  and  Number  of  Cylinders.  Steam  engines  may 
have  one,  two,  or  three  cylinders  side  by  side,  all  using  high 
pressure  steam. 

Two-cylinder  engines — twin  engines,  mostly  horizontal — are 
used  as  colliery  winding  and  haulage  engines  or  steelworks 
rolling  mill  engines. 

Three-cylinder  engines — 'triple  engines,  mostly  horizontal — are 
used  as  steelworks  rolling  mill  engines. 

Engines  in  which  the  steam  expands  in  two,  three  or  four 
consecutive  stages  are  called  compound  engines,  triple-expansion 
engines  and  quadruple-expansion  engines  respectively.  Some 
triple-expansion  engines  have  two  low-pressure  cylinders  and  are 
therefore  four-cylinder,  triple-expansion  engines. 

The  two  cylinders  of  a  compound  steam  engine  may  be  ar- 
ranged one  behind  the  other — a  tandem  engine,  or  side  by  side — 
a  cross  compound  engine,  or  with  horizontal,  high-pressure  and 
vertical,  low-pressure  cylinders — an  angle  compound  engine. 

329 


330 


PRACTICE  OF  LUBRICATION 


2.  Types  of  Valves.  Many  types  of  valves  are  in  use,  bnt  they 
may  be  divided  into  four  main  groups,  as  follows: 

1.  Slide  Valves. 

2.  Corliss  Valves. 

3.  Piston  Valves. 

4.  Drop  Valves  or  Poppet  Valves. 

Slide  valves  are  not  used  in  single-cylinder  engines  of  over  125 
horsepower,  because  they  are  inefficient. 

In  compound  and  triple-expansion  engines  slide  valves  may  be 
used  for  the  intermediate  and  low-pressure  cylinders  in  sizes 
from  50  to  750  horsepower  per  cylinder. 

Slide  valves  can  only  be  used  for  low  superheat,  as  their  un- 
symmetrical  shape  causes  warping.  They  can,  however,  be 
used  at  high  speed,  as  they  are  positively  operated. 

Corliss  valves  are  rarely  used  in  engines  below  125  horsepower 
in  size,  as  they  are  not  so  adaptable  to  the  high  speeds  at  which 
small  engines  operate.  They  can  be  employed  with  moderate 
superheat. 

Piston  valves,  notwithstanding  their  rather  low  efficiency,  are 
used  even  for  very  large  power  units,  as  they  can  be  operated  at 
high  speed,  with  high  steam  pressure,  and  high  steam  tempera- 
ture, and  are  very  reliable  for  severe  service,  as  in  colliery  wind- 
ing engines  and  steel  works  rolling  mill  engines.  They  are  largely 
used  in  marine  engines  and  for  locomotives. 

Drop  valves  are  used  for  the  highest  powers,  on  account  of  their 
great  efficiency;  they  are  not  used  for  power  units  below  125 
horsepower,  for  the  same  reason  as  given  under  Corliss  Valves. 
Drop  valves  can  be  operated  with  high  steam  pressure  and  high 
steam  temperature,  at  higher  speeds  than  the  Corliss  valve,  but 
not  at  such  high  speeds  as  the  piston  valve. 

Land  Engines. — In  Table  No.  14  is  shown  for  the  different 
types  of  valves:  the  normal  range  of  steam  pressure,  maximum 

TABLE  No.  14 


Valves 


Steam 


*lax' 


R.P.M. 


H.P. 

per  cylinder 


.  No.  of  cylinders 


Horizontal 


Vertical 


|                                         ; 

1    • 

Slide  

60  to  120 

450 

350  to  60 

Up  to  125 

1 

1 

Corliss.  .  .  . 

80  to  160 

525     !  150  to  60 

125  to  2000 

1,  2  or  4 

I,2or3 

Piston...  .  .  . 

I  90  to  200 

600       500  to  90 

Up  to  3000 

1,  2  or  3 

1,2  or  3 

Drop      or 

j 

• 

poppet  .  .  . 

,120  to  200 

600       180  to  90 

125  to  3000 

1  or  2 

STKAM    KXdINES 


331 


steam  temperature  permissible  revolutions  per  minute,  horse- 
power per  cylinder,  number  of  cylinders  employed  in  horizontal 
as  well  as  vertical  land  engines. 

In  Table  No.  15  is  shown  the  most  frequent  combinations  of 
valves  employed  in  single-cylinder  engines,  twin  engines,  triple 
engines,  compound  engines  and  triple-expansion  engines  as 
used  for  land  purposes. 

TABLE  No.  15 


High-pressure 
cylinder 

|    Intermediate- 
pressure 
cylinder 

One  low-            Two  low- 
pressure              pressure 
cylinder              cylinders 

f     Slide 

i 

Corliss 

Sinnle-cim  nder  engines  .    \\     _,. 
Piston 

•--•*-j/;'     111   ",  ;  ; 

Drop 

.  i  .   j 

Slide 

Twin  engines. 
Two  high-pressure  cyls. 
side  bv  side 

Corliss 
Piston 

!  (Colliery  winding  and  haulage  engines, 
steel  works  rolling  mill  engines) 

Drop 

;::;  ,;'-:'• 

Triple  engines.                    f      s]ide 

(Steel  works  rolling  mill  engines) 

Three      high-pressure      {     p{^ 

• 

cyls.  side  by  side  I  1 

. 

»  "     {•••:. 

•  -     ,  ,           [ 

. 

Corliss 

Corliss 

Piston 

Piston 

Compound  engines.  ..... 

Drop 

I'-     •  «  '" 

Drop 

Corliss 

.  ;  :.'  >>•}-•; 

Slide 

Piston 

1 

Slide 

Piston 

;  •'":•    •' 

Corliss 

Triple-expansion      en- 

gines      f    Corliss 

Corliss            Corliss 

Corliss 

Corliss             Slide 

Three  cylinders 

\    Corliss 
Piston 

Slide               Slide 
Piston             Piston 

Piston 

Piston              Slide 

Corliss 

Corliss            Corliss 

Corliss 

Four  cylinders  "VT.  •  '; 

Corliss 
Corliss 

Corliss 
Slide 

Slide 
Slide 

Slide 
Slide 

Piston 

Piston              Slide 

Slide 

Marine  Engines. — Small  marine  engines  are  compound  en- 
gines, say  below  100  H.P.  for  single  units.  The  vast  majority 
are,  however,  triple-expansion  engines.  Single  units  above  3,000 
I. H.P.  are  frequently  triple  expansion,  fo.ur  crank  engines,  with 
one  high  pressure,  one  intermediate  pressure  and  two  low  pres- 
sure cylinders. 


332  PRACTICE  OF  LUBRICATION 

Single  units  above  4,000  I.H.P.  are  frequently  quadruple 
expansion  engines,  with  one  high  pressure,  one  first  intermediate, 
one  second  intermediate,  and  one  low  pressure  cylinder. 

The  valves  belonging  to  the  high  pressure  cylinder  are  practi- 
cally always  piston  valves.  Piston  valves  are  also  generally 
used  for  the  intermediate  pressure  cylinder,  but  sometimes  slide 
valves  are  used.  Slide  valves  are  generally  used  for  the  low  pres- 
sure cylinder. 

Practically  all  marine  steam  engines  are  of  the  inverted  verti- 
cal type;  only  a  few  have  the  cylinders  and  valves  lying  at  an 
angle,  as  is  the  case  with  some  paddle  steamers. 

Steam  Pressure.  In  modern  marine  steam  engines  high  steam 
pressures  are  employed,  being  usually  from  180  Ib.  to  200  Ib. 
per  square  inch. 

In  the  vast  majority  of  cases  saturated  steam  is  employed, 
but  during  recent  years  superheated  steam  has  come  into  use 
very  largely  on  the  Continent,  the  maximum  steam  temperature 
at  the  engine  stop  valve  being  650°F. 

The  Revolutions  per  Minute  of  marine  steam  engines  are  largely 
governed  by  considerations  affecting  the  propeller  efficiency, 
and,  therefore,  do  not  vary  much  for  engines  above,  say,  1,000 
H.P.,  being  generally  between  80  and  90  R.P.M. 

In  the  case  of  launches,  higher  speeds  are  frequently  used  and 
with  consequent  lower  propeller  efficiency.  Some  large  naval 
ships  have  been  constructed  with  high  speed,  short  stroke  en- 
gines, the  maximum  speed  however  seldom  exceeding  130  R.P.M. 

Having  now  classified  the  various  types  of  steam  engines,  the 
subject  will  be  treated  under  the  following  headings: 

STEAM 

OIL  IN  EXHAUST  STEAM  AND  FEED  WATER 

OIL  IN  BOILERS 

METHODS  OF  LUBRICATION 

LUBRICATORS 

LUBRICATION 

DEPOSITS 

CORLISS  VALVE  ENGINES 

COLLIERY  WINDING  ENGINES 

UNIFLOW  ENGINES 

MARINE  ENGINES 

CYLINDER  OIL  CONSUMPTION 

SELECTION  OF  OIL 

TESTING  CYLINDER  OIL 

PHYSICAL  AND  CHEMICAL  TESTS 

TALLOW  MIXTURES  AND  SEMI-SOLID  GREASES 

LUBRICATION  CHART 


STEAM  ENGINES  333 

STEAM 

The  range  of  steam  pressure  employed  for  different  engines  is 
given  in  Table  14,  page  330.  Table  16  shows  temperatures  of 
saturated  steam  corresponding  to  various  pressures: 

TABLE  16. — PRESSURES  AND  CORRESPONDING  TEMPERATURES  OF  SATURATED 

STEAM 

Gauge  pressure,  Temperature, 

Ib.  per  sq.  in.  °F. 

60  307 

80  324 

100  338 

120  350 

140  360 

160  370 

180  379 

200  388 

220  396 

Dry  or  Wei  Saturated  Steam. — When  the  steam  leaves  the  boiler 
in  a  dry  condition,  it  is  called  dry  saturated  steam,  but  under 
certain  conditions,  for  instance,  when  the  boiler  is  forced  above 
its  normal  capacity  or  if  the  water  level  in  the  boiler  is  too  high, 
the  water  boils  violently;  priming  takes  place,  and  the  spray  or 
foam  from  the  water  surface  goes  out  with  the  steam,  which  in 
this  condition  is  called  wet  saturated  steam. 

It  is  in  order  to  prevent  the  bulk  of  this  water  from  being 
carried  over  with  the  steam,  that  various  so-called  anti-priming 
devices  are  frequently  employed.  If  the  steam  pipe  is  long  or 
not  properly  covered,  a  fair  amount  of  steam  will  be  cooled  and 
condensed  into  water  which  is  carried  along  with  the  steam  to- 
ward the  steam  engine,  together  with  any  water  that  may  have 
been  carried  over  from  the  boiler.  Therefore,  the  steam  pipe 
should  be  covered  with  insulating  material,  to  minimize  conden- 
sation. Water  in  the  steam  should  be  taken  out,  as  far  as  pos- 
sible, by  a  steam  separator.  But  where  the  steam  is  very  wet, 
it  is  difficult  even  with  a  good  separator  to  prevent  some  of  the 
water  from  entering  the  steam  engine. 

Superheated  Steam. — Saturated  steam,  in  passing  through  the 
heated  superheater  tubes,  is  heated  above  its  saturated  steam 
temperature  and  becomes  superheated  steam. 

The  water  which  has  been  carried  over  from  the  boiler  during 
periods  of  priming,  contains  impurities,  either  solid  impurities 
or  salts  in  solution.  When  priming  ceases  this  water  evaporates  in 
the  superheater  and  the  impurities  will  accumulate  in  the  super- 


334  PRACTICE  OF  LUBRICATION 

heater  tubes,  in  the  form  of  a  dry  dust,  which  gets  blown  over 
with  the  steam  into  the  engine  and  interferes  with  lubrication. 

The  steam  separator  tends  to  remove  not  only  water  but  also 
rusty  scale  and  impurities  which  are  carried  over  from  the  boiler 
or  which  break  loose  from  the  inside  of  the  steam  pipes,  also  fine 
oxidized  scale  from  the  inside  of  the  superheater  tubes  which  gets 
carried  over  in  the  form  of  a  fine  black  dust. 

Cutting  and  scoring  of  cylinders,  valves,  and  valve  faces  is 
sometimes  experienced  shortly  after  starting  up  a  new  engine. 
It  is  seldom  due  to  lack  of  lubrication  or  to  the  quality  of  the 
cylinder  oil  used,  but  in  most  cases  it  can  be  accounted  for  by  the 
steam  line  not  being  properly  blown  through  and  cleansed  from 
scale,  foundry  sand,  rust,  and  the  like.  It  is  obvious  that  the 
entrance  of  such  impurities  into  the  steam  engine  will  cause 
trouble,  and  the  utmost  care  should  be  taken,  when  starting  new 
steam  engines,  that  the  pipe-lines  from  the  boilers  to  the  engines, 
as  well  as  the  internal  spaces  in  the  valve  chests,  cylinders,  and 
steam  connections  between  the  cylinders,  shall  be  thoroughly 
cleansed. 

The  importance  of  having  a  steam  trap  just  before  the  inlet 
for  the  steam  into  the  engine  is  not  sufficiently  appreciated  by 
most  steam  users.  If  no  steam  separator  be  fitted,  it  is  obvious 
that  solid  matters  from  the  steam  line  or  the  boilers  will  have  free 
access  to  'the  engine,  which  often  results  in  the  necessity  for 
early  repairing  of  cylinders  and  refacing  of  valves,  etc. 

OIL  IN  EXHAUST  STEAM  AND  FEED  WATER 

A  portion  of  the  oil  used  for  lubricating  the  steam  engine  cylin- 
ders and  valves  will  pass  out  through  the  valve  rod  and  piston 
rod  glands,  but  the  greatest  portion  will  leave  the  engine  with,  the 
exhaust  steam  and  will  be  present  in  the  form  of  oil  in  suspension 
or  oil  in  emulsion. 

Oil  in  suspension  consists  of  oil  globules  that  are  fairly  easily 
removed  from  the  steam  by  the  exhaust  steam  oil  separator. 
The  globules  of  oil  which  are  not  extracted  from  the  steam  in 
the  separator  will,  in  the  case  of  condensing  engines,  mix  with 
the  condensed  steam  and  reach  the  hot  well,  where  the  greater 
portion  will  rise  to  the  surface  in  the  form  of  " float"  oil  which 
can  be  skimmed  off. 

A  final  safeguard  may  be  provided  in  the  form  of  a  feed  water 
filter,  the  filter  medium  being  cloth,  sand,  wood-wool,  etc.,  which 
will  retain  the  globules  of  oil  in  suspension.  The  filter  gradu- 
ally becomes  fouled  with  the  oil  and  the  difference  in  pressure 


STEAM  ENGINES  33.5 

of  the  feed  water  on  either  side  becomes  greater  and  greater.  If 
the  fouling  of  the  filter  be  allowed  to  proceed  too  far,  the  danger 
arises  that  the  collected  matter  may  be  swept  through  and  carried 
into  the  boilers.  If  a  pressure  gauge  be  fitted,  it  shows  the  differ- 
ence in  pressure  before  and  after  the  filter;  and  the  engineer  will, 
from  experience,  soon  become  acquainted  with  the  maximum 
difference  in  pressure  permissible. 

In  marine  practice  the  danger  of  the  pressure  becoming  too 
high  is  particularly  great  where  the  feed  water  pump  is  directly 
driven  by  the  main  engines,  as  in  event  of  the  engines  racing, 
the  increased  speed  of  the  feed  water  will  certainly  tend  to  clear 
out  the  oil  from  the  filter  and  carry  it  straight  into  the  boilers. 

Asbestos  fibre  is  said  to  be  capable  of  almost  entirely  breaking 
up  the  emulsified  particles  of  oil  and  water,  and  of  thus  extract- 
ing the  greater  portion  of  even  emulsified  oil,  but,  so  far,  experi- 
ments with  such  filtering  material  have  not  led  to  any  practical 
solution  of  this  question,  as  asbestos  fibre  is  both  costly  to  renew 
and  costly  to  clean. 

Oil  in  emulsion  consists  of  minute  particles  of  water  (less  than 
Y^  o  >  o  o  o  inch  in  diameter) ,  coated  with  an  oil  film .  They  are  so  fine 
that  they  float  in  the  steam  and  consequently  the  exhaust  steam 
oil  separator  will  only  remove  a  portion  of  the  emulsified  oil.  The 
greater  portion  of  the  oil  in  emulsion,  therefore,  mixes  with  the 
condensed  steam,  which  assumes  a  milky  appearance.  The 
greater  the  amount  of  oil  the  more  milky  will  the  water  be. 

Whereas  oil  in  suspension,  as  above  mentioned,  is  fairly  easily 
removed  in  the  hot  well  or  in  the  feed  water  filters,  not  so  with 
the  oil  in  emulsion.  The  particles  are  so  small  that  they  will  not 
rise  to  the  surface  in  the  hot  well,  and  the  filtering  medium  in  the 
feed  water  filter  will  not  be  able  to  retain  them. 

EXHAUST  STEAM 

In  non-condensing  steam  engines  the  steam  passes  out  into 
the  atmosphere,  or  it  may  be  used  for  the  purpose  of  heating  the 
premises,  for  drying  purposes,  or  for  heating  the  feed  water  in 
feed  water  heaters.  The  presence  of  oil  in  the  heating  or  drying 
apparatus  reduces  its  heating  capacity  very  considerably. 

In  condensing  engines  the  steam,  when  leaving  the  engine,  is 
condensed  either  by  the  jet  condensing  or  the  surface  condensing 
system. 

Jet  Condensing  System. — The  exhaust  steam  on  entering  the  jet 
condenser  meets  numerous  jets  of  cold  water.  The  cold  water 
condenses  the  steam  into  warm  water  which  by  me^ans  of  a  pump 


330  PRACTICE  OF  LUBRICATION 

is  taken  from  the  condensing  chamber  and  delivered  into  the 
hot  well,  from  which  a  small  portion  of  the  water  is  taken  away 
by  the  boiler  feed  pump  for  boiler  feed  purposes.  The  bulk  of 
the  water,  however,  is  either  allowed  to  waste,  or,  where  only  a 
limited  supply  of  cooling  water  is  available,  it  is  passed  through  a 
cooling  tower,  where  it  is  cooled,  so  that  it  can  be  used  over  and 
over  again.  A  large  portion  of  the  cylinder  oil  will  separate  out 
and  present  itself  as  float  oil  on  the  surface,  which  can  be  skimmed 
off  from  time  to  time.  There  is  generally  very  little  chance  of 
any  cylinder  oil  reaching  the  boilers  where  the  jet  condensing 
system  is  employed. 

Feed  Water  Heaters. — Such  heaters  are  installed  in  numerous 
plants  ashore  and  generally  they  are  what  are  termed  ''contact 
feed  water  heaters"  in  which  the  steam  comes  in  direct  contact 
with  the  feed  water. 

Some  oils  form  an  emulsion  with  the  water  and  do  not  separate 
out  in  the  heater.  The  greater  the  quantity  of  water  contained  in 
the  heater  the  easier  it  will  be  for  the  oil  in  suspension  to  separate; 
but  to  get  the  separation  anywhere  near  satisfactory,  it  is  neces- 
sary to  use  a  pure  mineral  cylinder  oil.  Under  no  conditions 
should  the  oil  be  allowed  to  accumulate  in  large  quantities  in 
the  heater,  but  it  should  be  drained  or  skimmed  off  at  suitable 
intervals. 

It  is  also  good  practice  to  take  the  suction  of  the*  feed  pump 
from  a  point  as  far  below  the  surface  as  possible,  as  near  the  bot- 
tom the  water  is  generally  most  free  from  oil.  Limy  deposits 
which  accumulate  in  the  bottom  of  the  heater  should  never  be 
allowed  to  reach  the  level  of  the  suction  pipe. 

Surface  Condensing  Plant. — The  exhaust  steam  is  here  not  cooled 
by  direct  contact  with  the  cooling  water,  but  simply  passes  through 
the  condenser  chamber,  in  which  are  a  great  number  of  tubes 
through  which  cold  water  is  forced.  The  steam  is  cooled,  con- 
densed, and  pumped  into  the  hot  well,  whence  the  boiler  feed 
pump  takes  the  whole  of  this  water  and  delivers  it  back  into  the 
boiler,  where  it  is  converted  into  steam  and  starts  the  circuit 
afresh. 

All  the  oil  contained  in  the  exhaust  steam  will  accumulate  in 
the  hot  well,  'and  the  same  remarks  which  were  made  in  refer- 
ence to  contact  feed  water  heaters  apply  here  as  to  skimming  off 
the  float  oil  and  taking  the  feed  water  from  a  low  level  in  the  well. 
Also  here  oil  in  emulsion  will  be  carried  through  with  the  feed 
water,  and  will  enter  the  boiler  unless  eliminated  by  special 
means.  Surface  condensing  engines  in  land  service  are  compara- 
tively few  in  number,  but  are  used  to  some  extent  for  electric 


STEAM  ENGINES  337 

power  installations  and  the  like,  and  more  especially  where  town 
water  is  expensive;  also  for  ice-manufacturing  plants,  when  the 
condensed  water  is  afterward  used  for  ice  production  and  where 
any  trace  of  oil  would  make  the  ice  cloudy. 

If  a  feed  water  filter  could  be  invented  in  which  some  special 
form  of  filtering  material,  such  as  asbestos  fibre  or  some  other 
substitute,  was  employed,  capable  of  extracting  oil  in  emulsion, 
such  a  filter  would  be  welcomed  by  many  engineers,  as  it  would 
be  the  simplest  way  of  preventing  oil  being  carried  into  the 
boilers,  of  course  operated  in  connection  with  an  exhaust  steam 
oil  extractor  which  would  extract  the  bulk  of  the  oil. 

Example  15. — A  horizontal,  200-horsepower,  cross  compound, 
condensing  Robey  engine  was  using  a  common  black  cylinder  oil. 
The  engine  was  surface  condensing,  and  the  feed  pump  dis- 
charged the  water  through  a  filter  which  was  supposed  to  clear 
the  feed  water  from  oil.  After  passing  this  filter  the  feed  water 
went  direct  to  the  boilers.  The  consumption  of  cylinder  oil  was 
found  to  be  4  or  5  drops  per  minute,  and  if  the  feed  was  reduced, 
the  engine  started  groaning  and  grinding.  In  spite  of  all  that 
the  makers  of  the  filter  claimed,  oil  was  found  in  quantities  in  the 
boilers,  and  was  the  cause  of  a  most  serious  complaint  from  the 
insurance  companies. 

An  examination  of  the  boiler  deposit  showed  that  it  was  com- 
posed of  black  greasy  matters  and  boiler  scale.  The  boiler  scale 
was  partly  carbonates,  sulphates,  and  hydrates  of  lime  and  mag- 
nesia. After  introducing  a  pure,  mineral,  filtered  cylinder  oil 
it  was  found  possible  to  reduce  the  oil  consumption  to  one  drop 
in  70  seconds,  and  it  was  reported  that  a  marked  improvement  in 
the  boiler  conditions  took  place  at  once,  practically  all  the  oil 
separating  out  in  the  hot  well. 

Extracting  the  Oil. — The  oil  may  be  separated  from  the  exhaust 
steam  by  oil  separators  or  extracted  from  the  feed  water,  by 
chemical  or  electrical  treatment. 

Exhaust  Steam  Oil  Separators. — Some  exhaust  steam  oil  separa- 
tors are  very  large  reservoirs  fitted  with  baffle  plates,  in  which  the 
exhaust  steam  loses  its  velocity,  the  oil  and  moisture  separating 
out,  mainly  by  gravitation,  as  in  the  Baker  separator,  Fig.  147. 

The  exhaust  steam  enters  the  separator  through  branch  (1 
and  is  immediately  caught  and  deflected  to  the  lower  part  of  the 
separator  body  by  the  baffle  (2) .  This  baffle  besides  deflecting 
the  steam  also  tends  to  retain  such  globules  of  oil  and  water  as 
adhere  to  it  due  to  the  impinging  of  the  steam  against  its  surface. 
These  globules  eventually  collect  and  roll  down  baffle  (2),  find- 
ing their  way  into  the  well  in  the  separator  bottom.  A  large  free 
22 


338 


PRACTICE  OF  LUBRICATION 


passage  is  provided  under  the  baffle  (2),  which  allows  of  a  de- 
crease in  the  speed  of  the  steam  so  that,  by  the  time  the  steam 
is  passing  through  the  cleansing  angles  (3),  it  is  well  expanded 
and  the  temperature  lowered,  allowing  an  appreciable  condensa- 
tion to  take  place.  This  will  be  deposited  on  the  angle  bafflers 
in  chamber  (4) ,  whence  the  globules  trickle  down  on  to  the  sur- 
face of  the  water  in  the  separator  well  (5),  which  is  maintained 


FIG.   147.— Baker  oil  separator. 


at  a  constant  level  determined  by  the  position  of  the  oil  pipe 
(6),  through  which  the  caught  oil  is  discharged  by  gravitation  if 
the  steam  engine  is  non-condensing.  If  it  is  a  condensing  engine, 
the  oil  must  be  pumped  out  by  a  small  pump  which  should 
always  be  placed  at  least  24  inches  below  bottom  of  separator. 
.It  has  been  found  sometimes  that,  when  very  high  vacua  are 
carried  in  steam  condensing  plants,  the  exhaust  steam  is  not 


STEAM  ENGINES 


330 


freed  from  the  oil  and  water  contained.  The  cause  of  the  trouble 
needs  little  seeking,  as  the  air  which  is  always  contained  in  the 
condensing  plant,  and  which  constantly  leaks  into  the  system, 
expands  rapidly  with  the  higher  vacua.  Accordingly,  the  velo- 
city of  the  vapor  containing  the  air  is  so  great  through  the  oil 
extractor  that  any  oil  or  water  present  will  be  swept  out  from  the 


IMW 


M* 


MM 

Ng 

MM 


FIG.   148. — Princep's  oil  separator. 

separator.  Where  means  are  provided  so  that  oil  and  water  once 
taken  out  of  the  steam  cannot  again  enter  the  flow,  this  effect  of 
high  vacua  is  greatly  minimized.  This  point  has  been  kept  in 
mind  in  other  separators  which  are  more  compact  and  operate 
on  the  principle  of  splitting  up  the  steam  in  many  little  steam 
flows,  frequently  changing  their  direction  and  trapping  the  oil  by 
baffle  plates  which  are  so  designed  that  once  the  oil  has  been  re- 
moved from  the  steam,  it  cannot  be  picked  up  again  by  the  steam 


340  PRACTICE  OF  LUBRICATION 

but  gravitates  to  a  reservoir  in  the  bottom,  whence  the  oil  can 
be  removed  at  intervals. 

The  Princep's  oil  separator  (Fig.  148)  is  a  good  example,  illus- 
trating these  principles.  The  steam  is  allowed  to  expand  and 
reduce  its  velocity,  so  as  to  allow  the  solid  and  liquid  particles  to 
free  themselves  from  the  steam.  A  series  of  plates  is  suspended 
from  the  top.  These  plates  are  provided  with  a  number  of  holes. 
In  each  hole  is  inserted  a  ferrule  projecting  from  J^  inch  to  % 
inch  on  each  side  of  the  plate.  Through  these  ferrules  are  passed 
plates,  twisted  to  a  pitch  equal  to  the  distance  between  each 
plate.  The  steam  on  entering  the  separator  and  passing  through 
the  holes  strikes  the  twisted  blade,  which,  being  at  an  angle  of 
45°,  deflects  the  oil  and  water  on  to  the  face  of  the  plate.  The 
continual  action  of  the  steam  forces  the  deposit  on  the  plate  into 
the  bottom  chamber.  It  is  impossible  for  any  oil  collected  on  the 
first  plate  to  go  forward  to  the  second,  because  it  is  prevented 
from  doing  so  by  the  ferrule  which  surrounds  the  hole.  If  the 
first  deflecting  action  has  not  abstracted  all  the  oil  and  sediment, 
from  the  steam,  the  next  or  third  deflection  in  the  next  chamber 
will  nearly  always  do  so,  but  for  safety's  sake  a  few  more  plates 
are  fitted. 

The  makers  guarantee  that  there  shall  be  not  more  than  %  of  a 
grain  of  oil  per  gallon  of  water  .(condensed  steam) . 

FEED  WATER 

Chemical  Treatment. — Oil  in  emulsion  can  be  removed  from  the 
feed  water  by  adding  certain  chemicals  (alumina-soda  process) 
which  produce  a  flocculent  precipitate.  The  large  precipitated 
particles  take  hold  of  and  absorb  the  minute  particles  of  emulsi- 
fied oil,  so  that  subsequent  filtration  easily  clarifies  the  water. 

Feed  water  softening  and  purifying  plants  are  frequently  in  use 
where  the  greater  portion  of  the  feed  water  is  taken  from  the  town 
main  or  other  source  of  fresh  supply,  yet  in  a  great  many  large 
installations  where  surface  condensing  is  resorted  to,  and  where, 
therefore,  only  a  small  percentage  of  feed  make-up  is  required, 
feed  water  purifying  plants  may  be  installed  with  the  main  object 
of  entirely  freeing  the  water  from  cylinder  oil.  It  becomes  neces- 
sary in  such  cases  to  add  a  certain  amount  of  water  containing 
lime,  so  that,  by  virtue  of  the  chemical  processes,  the  oil  may  be 
thoroughly  eliminated.  This  treatment  has  the  disadvantage 
that  certain  chemicals  are  added  to  the  feed  water  which  are 
objectionable,  as  they  may  increase  the  tendency  of  the  boilers 
to  prime. 


STEAM  ENGINES  341 

Electrical  TrcMment. —  Another  method  is  the  electrical  treat- 
ment in  which  the  milky  feed  water  containing  the  emulsified  oil 
is  passed  through  a  tank  containing  two  rows  of  iron  plates;  an 
electrical  current  is  passed  through  the  water,  from  one  set  of 
plates  to  the  other.  The  result  is  that  the  minute  particles  of 
emulsified  oil  coagulate  and  combine  with  iron  oxide  (rust),  pro- 
duced from  the  plates,  forming  a  heavy  deposit  which  can  be  easily 
removed  by  subsequent  filtration  through  a  sand  filter. 

By  this  method  it  is  possible  to  remove  practically  every  trace 
of  oil  from  the  feed  water.  The  makers  (Davis  Perrett,  Ltd.) 
guarantee  that  the  contents  of  oil  shall  be  less  than  0.1  grain  per 
gallon,  the  consumption  of  electric  energy  being  1  B.T.U.  per 
1000  gal.  of  water  treated. 

FEED  WATER  SOFTENING.— li  certain  chemicals  are 
added  to  hard  feed  water  containing  salts  of  lime,  magnesia, 
etc.,  some  of  the  lime  and  other  ingredients  are  precipitated 
and  are  taken  out  in  the  form  of  sludge,  whereas  the  remainder 
are  transformed  into  such  salts  in  solution  that  will  not  produce 
scale  inside  the  boiler.  In  small  plants  a  frequent  practice  is  to 
add  the  chemicals  to  the  hot  well  or  directly  into  the  feed  water 
on  its  way  to  the  boiler,  or  even  into  the  boiler  itself.  In  this 
case  a  great  deal  of  sludge  is  produced  which  necessitates  fre- 
quent "blowing  down"  of  the  boiler. 

The  best  method  of  adding  the  chemicals  is  to  have  an  inde- 
pendent feed  water  softening  plant,  so  that  the  water  after  treat- 
ment is  pumped  into  the  boiler  in  as  purified  a  condition  as 
possible,  the  sludge  precipitated  in  the  softening  plant  being- 
removed  by  filtration. 

Even  ifVthe  feed  water  has  been  so  treated  that  no  scale  is 
being  formed  in  the  boiler,  it  is  obvious  that,  as  only  clean  steam 
evaporates  away  from  the  boiler,  the  water  will  become  more  and 
more  concentrated  with  salts  in  solution  and  inclined  to  cause 
priming,  so  that  a  certain  amount  of  water  should  be  blown  out 
and  replaced  with  fresh  feed  water,  in  order  to  keep  the  boiler 
water  in  good  condition. 

Feed  water  when  treated  is  slightly  alkaline;  if  it  is  excessively 
alkaline,  the  boilers  prime  and  the  degree  of  alkalinity  should 
therefore  be  kept  as  low  as  possible. 

OIL  IN  BOILERS 

As  has  been  explained,  oil  may  be  introduced  in  the  feed  water 
either  in  the  form  of  minute  particles  of  oil  kept  in  suspension, 
or  as  minute  particles  of  water  coated  with  a  thin  film  of  oil  (oil 
in  emulsion). 


342  PRACTICE  OF  LUBRICATION 

When  entering  the  boiler,  the  oil  in  suspension  will  rise  to  the 
surface  more  or  less  rapidly;  and  even  if  hardly  appreciable  quan- 
tities of  such  oil  are  introduced,  it  will  almost  invariably  be 
noticed  on  the  plates  in  the  neighborhood  of  the  water  level. 
Much  of  this  surface  oil  on  the  boiler  water  level  can  be  disposed  of 
by  judicious  use  of  the  scum  cocks. 

The  presence  of  oil  in  emulsion  is,  however,  much  more  dan- 
gerous as  the  small  particles  of  emulsified  oil  have  only  a  very 
slight  tendency  to  rise.  They  combine  with  the  solid  matters 
in  the  boiler  water,  such  as  carbonate  of  lime,  carbonate  of  mag- 
nesia, rust  (which  is  always  introduced  with  the  feed  water  or 
comes  from  the  boiler  plates),  etc.  Through  this  combination 
with  these  heavier  solids,  the  state  of  affairs  soon  becomes  this: 
that  the  combined  particles  have  the  same  gravity  as  the  water, 
and  accordingly  rise  and  fall  with  the  eddy  currents  set  up  by 
circulation.  They  coat  the  under  side  as  well  as  the  upper  side 
of  tubes  and  flues  and  cling  to  the  hot  plates.  The  emulsified 
particles  of  oil  which  combine  with  the  iron  rust  generally  become 
so  heavy  that  they  sink  to  the  bottom. 

The  greasy  deposit  on  tubes  and  flues  has  the  effect  of  imme- 
diately retarding  the  flow  of  heat  through  the  plate.  If  the 
deposit  contains  a  sufficient  percentage  of  oil,  the  flow  of  heat 
may  be  retarded  to  such  an  extent  that  the  plate  becomes  over- 
heated and  the  deposit  begins  to  decompose,  the  layer  in  contact 
with  the  hot  plate  giving  off  various  gases  which  blow  the  outer 
part  up  to  a  spongy,  leathery  mass,  which  by  reason  of  its  porosity 
retards  the  flow  of  heat  even  more  than  the  thin  greasy  deposit. 
The  plate  subsequently  becomes  healed  to  redness,  and  being  unable 
to  withstand  the  pressure  of  the  steam  collapses.  At  the  same  time  the 
temperature  has  increased  to  such  an  extent  that  the  oil  is  burned 
away  from  the  deposit,  leaving  behind  an  apparently  harmless 
deposit,  containing  the  solid  particles  with  which  the  oil  originally 
became  combined. 

It  has  been  found  that  new  boilers  with  clean  flues  are  more 
affected  by  oil  than  are  boilers  in  which  a  certain  amount  of  scale 
is  present.  Many  cases  have  been  known  where  new  boiler 
furnaces  have  come  down  when  the  thickness  of  the  coating  of 
grease  has  probably  been  less  than  one-thousandth  of  an  inch.  A 
coating  of  oil  of  this  thickness  will  increase  the  temperature 
of  the  boiler  plates  several  hundreds  of  degrees  F.  even  with  a 
moderate  rate  of  evaporation. 

A  series  of  experiments  was  carried  out  by  the  late  Mr.  Wm. 
Parker,  Engineer  in  Chief  to  the  Lloyd's  Registry,  with  a  view  to 
determining  how  far  the  conductivity  of  steel  and  iron  plates  is 


STEAM  ENGINES  343 

affected  by  oil  films.  His  experiments  proved  that  if  an  open 
steel  dish  was  painted  with  three  or  four  coats  of  greasy  deposit 
taken  from  the  bottom  of  a  boiler  in  which  a  furnace  collapse  had 
occurred,  mixed  with  a  little  cylinder  oil,  it  was  possible  to  burn 
the  bottom  of  the  dish  before  the  water  in  it  boiled.  ^  , 

Example  16. — The  following  interesting  example  is  an  excerpt 
from  a  paper  read  before  the  North  East  Coast  Institution  of 
Engineers  and  Shipbuilders,  1904-5,  by  Mr.  D.  B.  Morison,  and 
speaks  for  itself. 

A  disastrous  accident  came  under  my  notice  some  time  ago  in 
which  the  furnaces  of  a  passenger  steamer  collapsed  in  mid-ocean. 

The  boilers  were  apparently  clean,  with  no  appreciable  scale  on 
any  part.  The  principal  cause  of  the  accident  was  the  use  of  a  very 
inferior  oil  for  swabbing  the  rods  and  lubricating  the  auxiliary  engines. 
The  oil  became  emulsified  with  the  feed  water  and  being  therefore 
unfilterable  passed  directly  into  the  boilers.  The  deposit  scraped  from 
the  furnaces  and  other  parts  of  the  boiler  was  analyzed  by  Mr.  J.  B. 
Dodds  of  Newcastle-on-Tyne,  who  reports  as  follows: 

Deposit  from  Furnace  below  Level  of  Fire 

Calcic  sulphate 2.51    per  cent. 

Calcic  oxide 0 . 852  per  cent. 

Magnesic  oxide 7 . 33    per  cent. 

Ferric  oxide 10. 11    per  cent. 

Zinc  oxide 7 . 102  per  cent. 

Insoluble  matter,  chiefly  sand,  dirt,  etc 2.55    per  cent. 

Free  oil,  only  mechanically  held  by  above  constitu- 
ents    66 . 76    per  cent. 

Oily  matter,  combined  with  oxides  of  magnesia,  iron 

and  zinc 2 . 95    per  cent. 


Total : 100 . 164  per  cent. 

"Remarks. — The  very  dark  color  of  this  sample  is  due  to  the  ab- 
normal quantity  of  oil  present.  This  quantity  is  so  great  that  it  must 
have  materially  affected  the  transmission  of  heat  to  the  water." 

Deposit  from  Shell  at  Water  Level 

Calcic  sulphate ': .' .  . .  .'./.' 0 . 788  per  cent. 

Calcic  oxide 1 . 816  per  cent. 

Magnesic  oxide i'.'i]  l^V  9.62    per  cent. 

Ferric  and  ferrous  oxide 11 .04    per  cent. 

Zinc  oxide 16 . 87    per  cent. 

Insoluble  matter,  chiefly  sand,  dirt,  etc 4 . 34    per  cent. 

Free  oil,  only  mechanically  held  by  above  constitu- 
ents    41 . 04  per  cent. 

Oily  matter,  chemically  combined  with  above 

oxides 14 . 49  per  cent. 

Total 100 . 004  per  cent. 


344  PRACTICE  OF  LUBRICATION 


Deposit  Scraped  from  Furnace  Crowns 

Calcic  sulphate 69 . 9    per  cent. 

Magiiesic  oxide 8 . 55  per  cent. 

Ferric  oxide 3 . 55  per  cent. 

Zinc  oxide 4.5    per  cent. 

Insoluble  matter,  which  consists  largely  of  more  cal- 
cic sulphate,  with  sand,  dirt,  etc 8 . 15  per  cent. 

Free  oil,*  only  mechanically  held  by  above  constitu- 
ents   0.77  per  cent. 

Oily    matter,    chemically    combined   with    above 

oxides 4.6  per  cent. 


Total 100.02  per  cent. 

*  On  furnace  crowns  which  have  been  overheated  there  are  generally  only 
evidences  of  oil  having  been  there. 

Deposit  from  Under  Side  of  Tubes 

Calcic  sulphate 3 . 93  per  cent. 

Calcic  oxide 1.1  per  cent. 

Magnesic  oxide 5 . 78  per  cent. 

Ferric  oxide 1 1 . 04  per  cent. 

Zinc  oxide 15.31  per  cent. 

Insoluble  matter,  sand  and  dirt 8 . 38  per  cent. 

Free  oil,  only  mechanically  held  by  above  oxides ...  20 . 23  per  cent. 
Oily    matter,     chemically    combined    with    above 

oxides. 34. 104  per  cent. 

Total 99 . 874  per  cent. 

"Report. — My  examination  of  the  sample  of  cylinder  oil  would  lead 
me  to  infer  that  any  injury  found  was  due  to  the  presence  of  a  large 
quantity  of  oil  in  the  boiler,  and  that  this  quantity  may  have  been  in- 
creased by  the  use  of  an  oil  deficient  in  lubricating  power,  necessitating 
its  use  in  large  quantities. 

"The  comparatively  small  percentage  of  ferric  oxide  (peroxide  of 
iron)  in  these  samples  would  show  that  the  iron  surfaces  had  been  only 
very  slightly  affected  as  far  as  corrosion  or  oxidation  is  concerned. 
The  presence  of  zinc  oxide  in  decided  quantity  would  indicate  that  zinc 
had  been  the  medium  used  to  protect  the  boiler  against  corrosion  or  oxi- 
dation, and  that  it  had  successfully  effected  its  purpose. 

(Signed)  JOHN  BKADBURN  DODDS." 

When  a  boiler  has  become  contaminated  with  oil,  it  should  be 
washed  out  in  the  usual  manner,  then  filled  with  water  contain- 
ing 0.5  Ib.  of  soda  ash  per  boiler  horse  power.  The  water  should 
be  kept  boiling  at  atmospheric  pressure  for  24  hours,  then 'drawn 
off,  and  a  thorough  washing  of  the  boiler  should  follow. 


STEAM  ENGINES  345 

METHODS  OF  LUBRICATION 

Points  of  Application. — In  order  to  lubricate  the  internal  parts 
of  steam  cylinders  and  valves,  cylinder  oil  is  introduced  at  one 
or  several  of  the  following  points : 

1.  Direct  to  the  steam  chest. 

2.  Direct  to  the  valves. 

3.  Direct  to  the  cylinders. 
4. -Direct  to  the  piston  rod. 
5.  Into  the  steam  line. 

1 .  Direct  to  the  Steam  Chest. — This  is  one  of  the  earliest  methods 
of  application.     In  the  case  of  slide  valves  oil  is  usually  intro- 
duced so  that  it  drops  directly  over  the  valve  face.     In  the  case 
of  Corliss  valves  or  drop  valves  (Fig.  154 A),  oil  is  usually  intro- 
duced at  two  points  halfway  between  valves  and  steam  pipe 
(4).     The  flow  of  steam  going  to  the  right  carries  along  with  it 
the  oil  to  the  right-hand  valve  (66),  and  the  flow  of  steam  going 
to  the  left  carries  the  oil  to  the  left-hand  valve  (6a).     The  oil, 
after  passing  the  valves  enters  the  cylinder  and  provides  lubrica- 
tion for  the  piston  (1);  finally  the  oil  reaches  and  lubricates  the 
exhaust  valves. 

2.  Direct  to  the  Valves. — Oil  is  delivered  at  one  point  at  the 
centre  of  the  Corliss  valve,  or  at  two  points,  one  at  either  end  of 
the  Corliss  valve.     It  is  the  ends  of  the  valve  that  require  most 
lubrication,  and  feeding  to  the  ends  direct  is  therefore  preferable 
to  feeding  at  the  centre,  in  which  case  the  flow  of  steam  sweeps 
the  oil  right  through  the  valve  without  any  lubrication  reaching 
the  valve  ends.     Piston  valves  are  sometimes  lubricated  by  two 
oil  feeds  in  this  manner,  one  feed  to  each  end  of  the  valve. 

3.  Direct  to  the  Cylinders. — Sometimes  in  the  case  of  large 
engines,  oil  is  introduced,  either  at  the  centre  of  the  cylinder,  or 
at  the  top,  or  bottom;  the  oil  thus  introduced  is  gradually  spread 
by  the  piston  over  the  cylinder  walls. 

4.  Direct  to  the  Piston  Rod. — Oil  is  introduced  direct  to  the  piston 
rod  externally,  that  is,  outside  of  the  piston  rod  gland,  either  by 
oil  dropped  from  a  lubricator  on  to  the  piston  rod,  or  by  an  oil 
swab  resting  on  the  rod.     The  oil  may  also  be  introduced,  par- 
ticularly  under   conditions   of  high  temperature  and  pressure, 
directly  into  the  piston  rod  gland  itself,  which  gives  a  greater 
certainty  of  the  oil  being  properly  distributed,  as,  when  the  oil 
is  applied  externally,  the  greater  portion  is  scraped  off  by  the 
gland  and  runs  to  waste. 

The  four  points  of  application  so  far  mentioned  are  direct, 
that  is,  the  oil  is  delivered  as  direct  as  possible  to  the  moving 


340  PRACTICE  OF  LUBRICATION 

parts  requiring  lubrication,  and  speaking  generally,  the  more 
"direct"  the  oil  is  fed,  the  less  satisfactory  is  its  distribution. 

There  is  this  disadvantage  that  as  cylinder  oil  is  very  heavy  in 
viscosity,  it  spreads  only  with  difficulty;  it  is  apt  to  overlubricate 
some  parts  and  not  reach  other  parts.  For  this  reason  a  great 
deal  of  oil  is  required  in  order  to  insure  that  a  complete  lubricating 
film  is  maintained  everywhere. 

Feeding  Oil  into  the  Steam  Line. — Thi  is  the  best  method  of 
application  and  embodies  an  entirely  different  principle,  as,  in- 
stead of  lubricating  the  various  parts  direct,  the  steam  itself  is 
lubricated. 

By  the  introduction  of  the  oil  into  the  main  flow  of  steam,  it  is 
possible  to  make  the  steam  carry  the  oil  to  all  parts  requiring 
lubrication,  in  fact,  the  steam  itself  is  made  a  lubricant.  The  oil 
is  introduced  preferably  on  the  boiler  side  of  the  engine  stop 
valve,  and  in  the  case  of  saturated  steam,  should  be  introduced  at 
least  18  inches  away  from  the  stop  valve. 

In  the  case  of  superheated  steam,  which  does  not  carry  the 
oil  so  well  as  saturated  steam,  it  should  be  introduced  not  more 
than  18  inches  before  the  engine  stop  valve.  In  cases  where  the 
superheat  is  very  high  and  where  the  steam  is  carried  around  the 
steam  cylinder  before  it  enters  the  valves  (usually  drop  valves) 
on  the  top  of  the  cylinder,  it  is  not  practical  to  introduce  the  oil 
before  the  engine  stop  valve,  as  it  would  be  precipitated  on  the 
way;  the  oil  is  then  introduced  directly  into  the  drop  valves  at 
a  point  where  the  flow  of  steam  will  break  up  the  oil  and  distrib- 
ute it  in  the  steam  passing  through  the  valves  every  time  they 
open. 

Atomizing  the  Oil. — It  is,  however,  not  sufficient  to  merely 
introduce  the  oil  into  the  steam  pipe  or  flow  of  steam,  as  the  oil 
then  is  merely  pushed  along  in  the  form  of  drops. 

The  best  method,  insuring  perfect  distribution,  is  the  atomizing 
method  by  which  the  oil  is  introduced  through  an  atomizer  (Fig. 
150)  into  the  centre  of  the  flow  of  steam.  The  steam  impinging 
with  great  velocity  (from,  say,  60  feet  to  150  feet  per  second) 
against  the  spoon  shaped  end  of  the  atomizer  will  squeeze  the 
oil  through  the  slits  in  the  atomizer,  so  that  the  oil  gets  thoroughly 
broken  up,  and  in  the  form  of  an  exceedingly  fine  spray  mixes  with 
the  steam. 

Various  atomizers  have  been  made  for  the  purpose  of  splitting 
up  the  oil  into  minor  particles,  for  example  the  oil  was  made  to 
ooze  out  from  the  perforated  end  of  a  tube,  but  the  small  holes 
(see  Fig.  149)  only  divided  the  oil  into  drops  sufficiently  small  to 


STEAM  ENGINES 


347 


pass  through  these  holes.     Other  forms  allowed  the  oil  to  be 
broken  up  over  sharp  edges. 

After  many  trials,  the  author  evolved  the  sawslit  type  of 
atomizer  illustrated  in  Fig.  150  (not  patented).  Its  introduc- 
tion has  saved  many  thousands  of  barrels  of  oil  and  many 


FIG.   149.— Atomizer. 


thousands  of  horse  power  that  previously  were  wasted.  When 
passing  the  slits,  which  should  not  be  more  than  >^2  incn  wide, 
the  oil  is  well  atomized,  and  entering  the  engine  it  lubricates 
the  spindle  of  the  engine  stop  valve,  making  this  valve 


FIG.   150. — Thomson's  atomizer. 

easy  to  operate.  It  lubricates  the  steam  valves  and  their 
spindles,  the  steam  throwing  down  a  slight  portion  of  the  oil  on 
these  points.  The  oil  is  thoroughly  distributed  in  the  form  of  a 
uniform  coating  over  the  piston,  piston  rings,  and  cylinder  walls. 
The  piston  rod  receives  its  proper  share  of  the  oil,  and  accordingly 


348 


PRACTICE  OF  LUBRICATION 


lubricates  the  piston  rod  gland  packing  from  the  inside,  which  is 
much  more  economical  and  efficient  than  lubricating  the  piston 
rod  from  the  outside. 

The  exhaust  valves  receive  their  share  of  lubrication,  and  the 
exhaust  steam,  if  it  be  carried  over  to  the  low  pressure  cylinder 
(in  the  case  of  a  compound  engine),  or  to  the  intermediate  pres- 
sure and  low  pressure  cylinders  (in  the  case  of  a  triple  expansion 
engine),  will  carry  over  finely  atomized  oil,  so  as  to  assist  in 
lubricating  these  cylinders.  Speaking  generally  it  will  be  found 
that  when  the  feed  of  cylinder  oil  is  ample  for  the  satisfactory 
lubrication  of  the  high  pressure  cylinder,  sufficient  oil  will  be 
carried  through  to  lubricate  successfully  the  remaining  cylinders. 


FIG.   151. — Two  oil  feeds  for  a  compound  engine. 

If  between  cylinders  of  a  compound  or  triple  expansion  engine 
there  are  large  receivers  which  may  perhaps  be  utilized  for  reheat- 
ing the  steam,  these  receivers  will  act  as  oil  separators,  in  which 
case  it  frequently  becomes  necessary  to  feed  oil  direct  to  the 
intermediate  and  low  pressure  engines;  but  this  should  be  done 
by  introducing  the  oil  into  the  steam  inlet  pipes  leading  to  these 
cylinders,  in  preference  to  feeding  the  oil  direct  into  the  valves 
or  cylinders. 

Ordinarily,  the  oil  feeds  to  the  intermediate  and  low  pressure 
steam  pipes  need  be  only  from  5  to  25  per  cent,  of  the  feed  into 
the  high  pressure  steam  main. 

Fig.  151  shows  how  the  two  feeds  from  a  mechanically  operated 
lubricator  mounted  on  a  compound  steam  engine  introduce  oil 
to  the  high  pressure  steam  pipe  and  low  pressure  inlet  pipe 
through  atomizers  carrying  the  oil  into  the  centre  flow  of  steam. 


STEAM  ENGINES  340 

Where  a  number  of  engines  or  pumps,  or  a  row  of  steam  ham- 
mers, each  separately  lubricated,  take  their  steam  from  the  same 
main,  admirable  results  may  be  accomplished,  in  the  way  of 
saving  in  oil  consumption  combined  with  better  lubrication, 
through  the  employment  of  one  lubricator  mounted  on  the  steam 
line  a  good  distance  away  from  the  first  unit  (sometimes  exceed- 
ing 20  feet),  and  feeding  the  cylinder  oil  through  an  atomizer 
into  the  central  flow  of  steam. 

The  steam,  as  previously  explained,  acts  as  a  carrying  medium 
for  the  lubricant,  and  each  unit  gets  a  share  of  the  oil  in  propor- 
tion to  the  quantity  of  steam  passing  through.  Atomizing  the 
oil  ami  using  the  steam  as  the  oil  spreading  medium,  results  in 
the  most  efficient  distribution  of  the  oil,  so  that  not  only  is  the 
friction  reduced,  but  also  the  quantity  of  oil  required  for  full 
lubrication.  As  this  method  relies  upon  the  velocity  of  the  steam 
to  atomize  the  oil,  it  will  be  understood  that  only  in  very  excep- 
tional cases  where  the  velocity  of  the  steam  is  too  low  will  it  fail. 
This  will  be  the  case  where  the  engines,  for  some  reason  or  other 
are  operated  at  considerably  less  than  half  load. 

When  the  oil  is  supplied  direct  to  the  various  parts,  it  is  very 
frequently  found  that  the  piston  rod,  particularly  under  high 
pressure  conditions,  is  poorly  lubricated.  The  rod  shows  evi- 
dence of  uneven  distribution  of  oil;  it  looks  scratched  all  over, 
and  has  that  peculiar  raw-polished  surface,  which  indicates  wear. 
Where  in  such  cases  the  atomization  method  is  ii  .oduced,  the 
oil  cups  furnishing  lubrication  to  the  outside  of  the  piston  rod 
can  usually  be  dispensed  with,  and,  due  to  the  better  lubrication 
of  the  piston  rod  from  the  inside,  the  surface  of  the  rod  will  soon 
assume  a  glossy  oily  appearance,  indicating  that  the  wear  has 
ceased  and  that  the  piston  rod  is  getting  a  hard  polished  skin. 

When  stopping  for  week-ends  or  for  longer  periods,  it  is  good 
practice  to  give  an  extra  large  quantity  of  oil  for  the  last  five 
minutes  the  engines  are  running.  This  will  give  a  nice  coating 
of  oil  to  all  the  internal  surfaces  and  prevent  the  formation  of 
rust,  which  otherwise  might  occur. 

Where  the  atomization  method  is  introduced,  it  is  not  unusual 
to  find  that  some  of  the  joints  between  the  point  of  entrance  of 
the  oil  and  the  valve  chest  commence  to  leak,  as  some  of  the  oil 
may  dissolve  deposits  and  dirt  in  the  joints,  which  will  therefore 
need  to  be  tightened  or  repacked  to  keep  steam  tight. 

Typical  Results  of  Using  the  Atomization  Method, — The  cyl- 
inder oil  should  be  introduced  on  a  length  of  steam  pipe  with  as 
few  bends  as  possible  before  it  enters  the  valve  chest,  and  there 
must  be  no  drains  which  might  trap  the  oil.  The  importance 
of  this  point  is  illustrated  in  Example  No.  17. 


350  PRACTICE  OF  LUBRICATION 

Example  17. — Four  steam  hammers  were  supplied  with  steam 
from  the  same  main,  and  a  sight-feed  lubricator  was  mounted  a 
good  distance  before  the  first  steam  hammer,  while  a  drain  pipe 
was  fixed  between  this  hammer  and  the  lubricator.  As  long  as 
all  hammers  were  in  full  swing  everything  went  well,  but  when 
only  one  hammer  was  working  the  flow  of  steam  was  so  small 
that  some  of  the  oil  was  not  properly  atomized,  but  dropped  to 
the  bottom  of  the  pipe  and  was  urged  along  the  steam  pipe,  and, 
reaching  the  drain,  dropped  down. 

After  the  position  of  the  lubricator  was  changed  to  a  place 
between  the  drain  and  the  first  steam  hammer,  no  further 
trouble  was  experienced. 

Example  18. — On  a  colliery  winding  engine  a  good  grade  of 
cylinder  oil  was  used,  the  consumption  being  1^  gallons  per  24 
hours.  The  oil  was  introduced  into  the  steam  pipe,  but  not 
through  an  atomizer.  The  Corliss  valves  were  grinding  slightly. 
After  fitting  an  atomizer,  the  grinding  immediately  stopped,  and 
the  consumption  was  reduced  to  %  gallon  per  24  hours'  work. 

After  twenty  months'  working  under  these  conditions  the  tool- 
marks  on  the  high  pressure  cylinder  were  not  worn  away  and  the 
colliery  manager  was  satisfied  that  no  other  method  of  lubrication 
would  have  kept  the  cylinders  in  such  remarkably  fine  order. 

Example  19. — A  cylinder  oil  of  good  quality  had  been  in  use  for 
some  time  with  only  fairly  good  results  on  a  "Robey  "  compound 
horizontal  engine,  the  oil  being  introduced  direct  into  the  steam 
chest  by  a  sight-feed  lubricator.  When  the  oil  was  introduced 
4  feet  away  from  the  cylinder  into  the  steam  pipe  from  a  mechan- 
ically operated  lubricator,  an  inspection  a  few  weeks  later  showed 
that  great  improvement  had  taken  place.  The  internal  wearing- 
surfaces  had  a  nice  oily  appearance  and  no  wear  was  noticeable. 
It  was  observed,  when  taking  out  the  piston,  that  the  thread  of 
nut  and  piston  rod  end  were  well  lubricated,  whereas  before  they 
used  to  be  dry,  and  difficulty  was  experienced  in  getting  the  nut 
off. 

Example  20. — Two  "Ruston  Proctor,"  horizontal,  cross  com- 
pound engines  were  lubricated  with  sight-feed,  hydrostatic  lubri- 
cators, feeding  cylinder  oil  into  the  valve  chest  of  high  pressure 
cylinder.  It  was  necessary  to  resort  to  " flushing"  of  the  low 
pressure  cylinders  through  tallow  cups  which  were  placed  on  the 
centre  of  the  low  pressure  cylinder  barrels.  After  altering  the  feed 
to  the  steam  pipe  and  employing  an  atomizer  (in  this  case  only 
4  inches  from  the  valve  chest,  owing  to  a  drain  in  the  steam  line), 
the  consumption  of  the  same  cylinder  oil  was  reduced  25  per 
cent,  and  the  " flushing"  of  the  low  pressure  cylinders  was  found 


STEAM  ENGINES  351 

to  be  unnecessary  as  the  oil,  atomized,  was  carried  over  with  the 
steam. 

Example  21. — Some  blowing  engines  on  an  ironworks  had  large 
D  slide  valves  (42  in.  by  48  in.  outside  dimensions)  with  8  in. 
travel.  Revolutions  per  minute  of  the  engine,  40;  steam  pres- 
sure, 60  Ib.  per  sq.  in.;  the  steam  superheated  to  450°F.  This 
engine  was  using  half-a-gallon  of  a  very  viscous  mineral  cylinder 
oil  per  24  hours'  run  and  the  slide  valve  at  times  jarred  very 
badly.  A  compounded  cylinder  oil  was  then  introduced,  but 
although  the  valve  worked  better,  yet  it  jarred  badly  at  times, 
and  the  defect  could  be  stopped  only  by  a  copious  supply  of  oil. 

After  this  an  atomizer  was  filled,  and  the  working  of  the  engine 
changed  at  once.  The  valves  subsequently  worked  very  smooth- 
ly, the  engine  giving  no  trouble,  and  the  consumption  of  the  same 
cylinder  oil  was  reduced  30  per  cent. 

Example  22. — A  colliery  fan  engine  (large  slide  valve  with  ex- 
pansion valve)  used  8  gallons  of  cylinder  oil  per  week  through 
sight-feed  hydrostatic  lubricators  and  tallow  cups. 

These  appliances  were  replaced  by  a  mechanical  lubricator, 
the  feed  entering  flush  with  the  inside  of  the  steam  pipe.  This 
alteration  made  it  possible  to  reduce  the  consumption  of  cylinder 
oil  to  4  gallons  per  week.  A  further  reduction  was  tried,  but 
the  amount  of  oil  had  to  be  increased  owing  to  the  vibration  of 
the  eccentric  rods,  which  indicated  that  the  valves  were  insuffi- 
ciently lubricated. 

Another  mechanical  lubricator  of  an  improved  type  was  then 
fitted  introducing  the  oil  through  an  atomizer  into  the  same  place 
as  before,  the  result  being  that  the  engines  ran  smoother  than 
ever,  and  the  oil  consumption  was  reduced  to  only  1^  gallons 
per  week. 

Example  23. — On  a  large  steam  engine  driving  an  air  com- 
pressor it  was  found  necessary  to  tighten  the  glands  two  or  three 
times  a  week,  when  the  oil  was  introduced  direct  into  the  valve 
chests.  After  the  lubricator  was  altered  to  feed  into  the  main 
steam  pipe  through  an  atomizer,  the  glands  required  to  be  tightened 
only  once  in  three  weeks. 

Example  24. — A  350-horsepower  fan  engine  in  a  colliery  con- 
sumed 3  gallons  per  day  of  common  cylinder  oil  fed  through  three 
mechanically  operated  lubricators,  having  a  total  of  eight  oil 
feeds,  feeding  direct  to  the  Corliss  valves.  In  addition,  it  was 
found  necessary  to  feed  extra  oil  to  the  ends  of  two  of  the  Corliss 
valves,  in  order  to  keep  them  silent. 

A  change  was  made,  feeding  a  good  quality  compounded  oil 
into  the  high  pressure  steam  pipe  through  an  atomizer,  and  the 


352  PRACTICE  OF  LUBRICATION 

improvement  in  lubrication  was  immediately  noticed.  The  two 
lubricators  were  discontinued;  the  consumption  was  gradually 
reduced  to  two  pints  per  day,  and  it  was  never  found  necessary  to 
feed  extra  oil  to  the  Corliss  valves. 

Example  25. — A  2-cylinder,  horizontal  rolling  mill  engine  was 
lubricated  with  a  common  straight  mineral  grade  of  cylinder  oil 
internally  and  for  the  piston  rod  guides.  Grease  was  used  on  the 
crank  pins,  eccentrics  and  main  bearings.  By  the  substitution 
of  a  good  grade  compounded  cylinder  oil  for  the  internal  lubri- 
cation introduced  through  atomizers,  and  an  engine  oil,  specially 
suited  to  the  work,  on  slides,  eccentrics,  crank  pin  and  main 
bearings,  a  great  reduction  in  the  power  required  to  overcome 
the  friction  in  the  engine  was  made. 

With  previous  oils  in  use,  the  engine,  with  all  load  off,  took 
94.2  I.H.P.  Five  weeks  after,  with  the  new  oils  in  use,  and  under 
exactly  similar  conditions,  the  engine  consumed  only  41.4  I.H.P. 
showing  a  reduction  of  56  per  cent,  in  the  power  necessary  to 
drive  the  engine  with  the  rolls  uncoupled.  The  average  tem- 
perature of  slides  above  room  was  reduced  from  33°F.  with 
the  old  oil  in  use  to  12.5°F.  with  the  new  oil,  showing  a  reduction 
in  rise  in  temperature,  due  to  friction,  of  20.5°F.  or  63  per  cent. 

The  cost  of  lubrication  was  reduced  by  19  per  cent,  with  the 
better  grade  oils  in  use,  the  actual  quantity  of  oil  required  being 
only  one-third  of  that  required  with  the  previous  oil. 

The  total  number  of  indicator  cards  taken  during  both  tests 
was  160,  every  set  of  cards  being  taken  simultaneously,  as  all 
pencil  motions  were  operated  electrically. 

Example  26. — Striking  differences  caused  by  lubrication  may 
often  be  noticed  on  long-stroke,  slow-speed  reciprocating  pumps, 
for  example,  Weir's  or  Woodeson's  type.  If  a  change  in  the 
cylinder  oil  be  made  to  a  better  grade,  or  if  the  method  of  lubri- 
cation be  improved,  the  change  will  immediately  result  in  a 
greater  number  of  strokes  per  minute,  and  a  smoother  and  more 
gliding  motion  of  the  rods,  the  reason  being  that  from  25  per 
cent.-50  per  cent,  of  the  indicated  horsepower  is  consumed  by 
friction. 

These  examples  show  that  a  decided  success  has  followed  the 
combination  of  mechanical  lubricators  with  atomizers  and  suita- 
ble grades  of  oil.  The  arrangement  must,  however,  in  each  case 
be  given  due  thought  and  consideration  to  ensure  good  results. 

LUBRICATORS 

The  Tallow  Cup. — The  earliest  form  of  lubricator  is  the  tallow 
cup,  consisting  of  an  oil  reservoir  with  a  filling  plug  at  the  top 


STEAM  ENGINES   •  353 

and  a  cock  at  the  bottom  for  emptying  the  oil  from  the  reservoir 
into  the  'cylinder,  or  valve  chest,  etc.  When  the  tallow  cup  is 
filled  with  oil  and  the  charge  flushed  into  the  engine,  most  of  it 
will  immediately  drop  to  the  bottom  of  the  cylinder  and  be  swept 
out  with  the  exhaust  steam,  within  the  next  few  strokes  of  the 
engine.  Then  the  engine  runs  on  what  little  oil  there  may  be 
left,  and  within  a  short  time  will  be  running  with  no  oil  at  all, 
until  such  time  as  the  engine  attendant  considers  it  necessary  to 
repeat  the  operation. 

When  the  tallow  cup  is  fixed  on  the  valve  chest,  most  of  the 
oil  never  reaches  the  cylinder.  It  finds  its  way  to  the  lower 
regions  of  the  valVe  chest,  mixes  with  any  condensation  which  may 
be  present,  and  is  drained  out. 

The  tallow  cup  still  survives  as  an  emergency  lubricator  for 
flushing  purposes,  when  extra  oil  is  required  in  places  where  no 
oil  feed  is  ordinarily  provided  for,  such  as  top  of  cylinders  or 
valve  chests,  etc.  Tallow  cups  are  also  still  used  for  feeding- 
oil  to  small  steam  pumps  and  the  like. 

As- regards  proper  lubricators  for  feeding  cylinder  oil,  there  are 
two  main  types  in  use:  the  Hydrostatic  Lubricator  and  the 
Mechanically  Operated  Lubricator. 

Hydrostatic  Lubricator  (Fig.  152). — The  lubricator  is  usually 
attached  to  the  steam  pipe  and  sometimes  to  the  steam  chest. 
Steam  through  pipe  (1)  enters  the  condenser  (2)  at  the  top  of  the 
lubricator.  In  this  condenser  the  steam  is  cooled  and  condensed 
into  water;  when  the  valve  (3)  is  open,  the  water  is  allowed  to 
flow  down  through  pipe  (4)  into  the  bottom  of  the  oil  reservoir 
(5).  The  incoming  water  displaces  the  oil  and  compels  .it  t° 
flow  down  through  the  pipe  (6),  through  the  adjusting  valve 
(7)  fitted  for  the  purpose  of  regulating  the  feed;  then  the  oil 
rises  through  the  water  in  the  sight-feed  glass  (8)  and  enters  the 
steam  pipe  (10)  through  the  delivery  pipe  (9): 

The  gauge  glass  (11)  shows  the  level  of  the  oil  inside  the  con- 
tainer. The  drain  cock  (12)  is  fitted  for  drawing  off  the  water 
before  the  lubricator  is  refilled  with  oil  through  filling  plug  (13). 

The  distance  from  the  steam  inlet  at  the  top  of  the  pipe  (1)  to 
the  top  of  condenser  (2)  should  be  at  least  18  inches  in  order  to 
get  sufficient  height  of  water  to  force  the  oil  through  the  lubri- 
cator. Sometimes  when  a  large  oil  feed  is  demanded  the  pipe  (1) 
is  made,  in  the  form  of  a  coil,  so  as  to  provide  increased  cooling 
surface  for  condensation. 

When  the  lubricator  is  exposed  to  draft  or  to  low  temperature, 
which  makes  the  oil  sluggish,  it  is  necessary  to  provide  additional 
water  pressure  by  means  of  longer  piping  above  the  condenser. 

23 


354 


PRACTICE  OF  LUBRICATION 


The  lubricator  must  be  started  every  time  the  engine  starts, 
and  it  must  be  stopped  each  time  the  engine  stops  or  it -keeps  on 
feeding  and  oil  is  wasted.  In  draining  off  the  condensed  water 
and  in  refilling  the  lubricator,  a  certain  amount  of  oil  is  usually 
wasted. 

The  oil  feed  is  affected  by  change  in  viscosity  of  the  oil.  It 
will  therefore  vary  with  the  engine  room  temperature,  and  also 


FIG.   152. — Hydrostatic  lubricator. 

every  time  the  lubricator  is  filled  with  fresh  oil.  The  oil  passes 
through  small  passages,  which  are  liable  to  be  partially  choked 
with  dirt,  thus  reducing  the  oil  feed.  For  these  reasons  it  is 
difficult  to  maintain  a  uniform  feed  with  a  hydrostatic  lubricator, 
more  especially  where  a  very  small  feed  is  desired.  A  uniform 
feed  of  oil,  however,  is  of  great  importance,  as  otherwise  the 


STEAM  ENGINES  355 

steam  is  either  charged  with  a  large  amount  of  oil — too  much,  or 
with  a  small  amount  of  oil — too  little. 

In  connection  with  hydrostatic  lubricators  the  following  points 
must  be  kept  in  mind. 

When  the  sight-feed  glass  is  inclined  to  get  smeared  with  oil, 
this  may  be  caused  by  the  oil  drops  being  very  large  or  the  sight- 
feed  glass  having  too  small  a  bore.  The  remedy  is  to  fit  a  wider 
glass,  or  solder  a  wire  on  to  the  feed  nipple,  so  as  to  guide  the  oil 
drops  centrally,  or  to  fill  the  glass  with  salt  water  or  glycerine. 
The  heavier  specific  gravity  of  these  liquids  causes  the  oil  drops 
to  rise  earlier,  i.e.,  the  drops  are  smaller  and  do  not  touch  the 
glass. 

Leakages  of  joints  and  packings  must  be  avoided,  as  they  inter- 
fere with  the  operation  of  the  lubricator,  which  is  very  sensitive. 

The  lubricator  must  be  filled  completely  with  oil  and  the  con- 
denser must  be  given  time  to  fill  up  with  water,  otherwise  steam 
will  enter  the  oil  reservoir  and  agitate  the  oil  and  what  is  known 
as  " churning"  occurs  in  the  sight-feed  glass.  When  churning 
takes  place  the  lubricator  must  be  emptied,  cooled,  filled  afresh 
and  time  allowed  for  the  condenser  to  fill  with  water. 

The  oil  drops  vary  in  size,  according  to  the  size  of  the  nozzle, 
the  gravity  of  the  oil  and  the  liquid  in  the  sight-feed  glass;  ordi- 
narily it  will  be  found  that  one  gallon  of  oil  will  feed  in  10,000  to 
24,000  drops. 

If  the  oil  is  fed  by  an  unreliable  lubricator,  or  if  the  oil  feeds  do 
not  introduce  the  oil  in  the  best  possible  manner,  more  oil  is 
required  to  provide  lubrication,  and  the  lubrication  will  not  be 
so  efficient  as  when  the  oil  is  properly  fed  and  applied. 

True  economy  in  the  lubrication  of  the  valves  and  cylinders  is 
obtained  by  feeding  a  minimum  quantity  of  the  correct  grade  of 
oil  to  the  working  parts  with  such  regularity  as  will  insure  an 
unbroken  oil  film  between  the  frictional  surfaces.  Such  economy 
can  never  be  secured  by  the  use  of  a  lubricator  which  feeds  inter- 
mittently or  irregularly. 

The  hydrostatic  lubricator,  which  is  still  largely  used  in  the 
United  States  has  in  other  countries  been  practically  superseded 
by  the  mechanically  operated  lubricator. 

Mechanically  Operated  Lubricators. — Mechanically  op- 
erated lubricators  are  operated  from  some  moving  part  of  the 
engine;  they  therefore  start  feeding  as  soon  as  the  engine  starts, 
and  stop  feeding  when  the  engine  stops,  and  they  feed  the  oil 
in  direct  proportion  to  the  speed  of  the  engine. 

Mechanically  operated  lubricators  preferably  have  sight-feed 
arrangements  for  each  oil  feed,  so  that  the  exact  quantity  of  oil 


356  PRACTICE  OF  LUBRICATION 

passing  through  the  various  delivery  pipes  can  be  observed. 
These  lubricators  should  be  so  constructed  that  each  feed  is 
independent,  subject  to  separate  adjustment  and  control.  Also, 
the  working  parts  should  not  be  liable  to  wear,  and  what  is 
especially  important,  all  the  working  parts,  valves,  etc.,  should  be 
easily  accessible  for  inspection  and  cleaning. 

In  order  to  insure  that  the  oil  pipes,  from  the  mechanically 
operated  lubricator  to  the  various  parts  of  the  engine  where  oil 
is  introduced,  shall  be  always  completely  filled  with  oil,  spring 
loaded  check  valves  should  be  fitted  at  their  extreme  ends.  The 
pipes  are  thus  always  filled  with  oil  and  lubrication  is  insured 
instantly  the  engine,  and  therefore  the  lubricator,  start  to  operate. 
This  check  valve  should  be  of  the  combined  check  and  vacuum 
valve  pattern,  in  order  to  prevent  the  oil  from  being  sucked  out 
of  the  lubricator  container  when  a  vacuum  is  formed  in  the  steam 
line  during  a  standstill.  If  the  oil  is  introduced  into  a  steam 
connection  where  a  partial  vacuum  exists  (for  instance  before  the 
low  pressure  cylinder  of  a  triple-expansion  engine)  it  is  essential 
that  a  valve  of  this  description  be  fitted. 

Care  should  be  taken  that  the  valve  does  not  leak,  and  that 
the  spring  is  strong  enough  to  keep  the  valve  on  its  seat  against 
the  vacuum  which  tends  to  open  it.  The  construction  and  op- 
eration of  mechanically  operated  lubricators  are  treated  in 
greater  detail  page  85. 

^      LUBRICATION 

The  internal  moving  parts,  comprising  valves,  valve  rods, 
piston  and  piston  rod,  are  exposed  to  the  action  of  hot  steam  and 
with  the  exception  of  the  valve  rod  and  piston  rod,  none  of  the 
internal  parts  are  exposed  to  view,  so  that  the  condition  of  lubri- 
cation cannot  easily  be  ascertained.  The  internal  lubrication  of 
steam  cylinders  and  valves  is  therefore  of  greater  importance 
and  more  difficult  than  the  lubrication  of  the  external  moving 
parts. 

Slide  Valve. — The  flat  surface  of  the  slide  valve  rubbing  against 
the  valve  face  is  difficult  to  lubricate,  particularly  in  the  case  of 
large  slide  valves.  In  some  cases,  oil  grooves  are  cut  in  the  valve 
or  in  the  valve  face,  in  order  to  assist  the  oil  in  spreading  all 
over  the  frictional  surfaces. 

The  pressure  between  the  valve  and  its  face  is  great,  parti- 
cularly with  " unbalanced"  slide  valves.  Improper  lubrication 
results  in  abrasion  and  cutting;  excessive  leakage  of  steam  takes 
place  and  wipes  away  the  lubrication  film  from  the  valve  face, 
necessitating  an  increased  consumption  of  oil.  Excessive  fric- 


STEAM  ENGINES  357 

lion  of  the  slide  valve  frequently  makes  the  valve  groan  during 
operation,  and  the  excessive  resistance  in  moving  the  valve  can 
usually  be  noticed  by  trembling  of  the  eccentric  rod. 

When  the  cover  from  the  slide  valve  chest  is  removed  and  the 
slide  valve  is  examined,  excessive  friction  is  always  indicated  by 
a  dryness  of  the  rubbing  surfaces,  showing  wear  and  streaks  of 
cutting  where  the  metallic  surfaces  have  eaten  into  one  another. 
It  is  important  that  the  cast  iron  in  the  valve  and  in  the  valve 
face  should  be  of  slightly  different  quality  or  hardness,  as,  if  the 
quality  is  practically  the  same,  they  do  not  work  well  together. 

Efficient  lubrication  of  the  slide  valve  produces  a  polished, 
glossy  surface  on  the  valve  face.  The  valve  operates  without 
noise ;  the  eccentric  rod  works  smoothly,  and  when  opened  up  for 
inspection  the  frictional  surfaces  show  a  complete  lubrication  film. 

Owing  to  the  large  flat  frictional  surfaces  of  slide  valves  and  to 
the  difficulty  of  getting  the  oil  thoroughly  introduced  between 
them,  and,  furthermore,  due  to  the  great  pressure  between  the 
valve  and  its  face,  it  will  now  be  understood  why  the  use  of 
slide  valves  is  limited  to  steam  pressures  of,  say,  125  Ib.  to  the 
square  inch,  and  a  maximum  steam  temperature  of,  say.  450°F., 
and  also  why  overloading  always  makes  lubrication  difficult. 
Experience  has  proved  that  when  the  oil  is  introduced  into  the 
steam  and  is  thoroughly  atomized,  the  oil  gets  much  better  dis- 
tributed and  has  in  many  cases  overcome  groaning  and  trouble 
with  slide  valves  where  the  direct  methods  of  lubrication  have 
failed  to  produce  good  results. 

Corliss  Valves. — The  Corliss  valve  operates  under  conditions 
very  similar  to  those  of  the  slide  valve,  as  it  has  a  reciprocating 
sliding  motion,  only  it  oscillates  over  a  cylindrical  surface  in- 
stead of  moving  over  a  flat  surface. 

Conditions  of  high  temperature  and  high  pressure,  therefore, 
affect  the  lubrication  of  the  Corliss  valve  in  the  same  manner  as 
they  affect  the  slide  valve.  Bad  lubrication  is  usually  noticed 
when  " feeling"  the  valve  stems.  As  *  the  admission  Corliss 
valves  are  not  positively  operated  during  the  closing  period,  bad 
lubrication  may  sometimes  be  indicated  by  the  valves  working 
sluggishly  or  even  "  sticking. "  Corliss  valve  engines  are  specially 
referred  to  page  368. 

Piston  Valves. — There  is  but  little  pressure  between  the  piston 
valve  and  its  cylindrical  sleeve,  the  pressure  being  mainly  that 
exerted  by  the  piston  rings.  Exposed  to  high  pressure  or  high 
temperature,  the  piston  valve  expands  uniformly,  and  the  pres- 
sure between  the  piston  rings  and  the  sleeve  remains  the  same. 
High  pressure  and  high  temperature,  .therefore,  have  little  effect 


358  PRACTICE  OF  LUBRICATION 

on  the  piston  valve,  nor  are  they  affected  by  overload,  and  conse- 
quently these  valves  can  be  operated  under  extreme  conditions. 

The  signs  of  good  or  bad  lubrication  are  similar  to  those  in- 
dicated by  slide  valves,  but,  owing  to  its  cylindrical,  balanced 
construction,  the  piston  valve  is  easier  to  lubricate.  It  is  impor- 
tant, however,  that  the  oil  be  well  distributed,  and  again  here 
experience  has  shown  that  this  can  best  be  done  by  the  atomiza- 
tion  method  of  lubrication. 

Drop  Valves. — The  drop  valve  lifts  from  its  seat  and  drops  on 
its  seat;  consequently,  no  lubrication  is  required,  except  for  the 
valve  spindle,  which  usually  is  very  long  and  has  a  very  short 
motion  in  its  guide.  The  clearance  between  the  valve  spindle 
and  its  guide  is  slight  so  that  it  is  important  to  have  perfect 
lubrication. 

The  oil  on  the  valve  spindle  is  stagnant  and  exposed  for  a  long 
time  to  the  high  temperature.  It  should  be  of  the  highest  quality, 
so  as  not  to  bake  into  a  carbonaceous  deposit,  which  might  cause 
sticking  of  the  valve. 

The  oil  should  preferably  be  sparingly  used  and  introduced  by 
means  of  the  steam,  so  as  to  be  uniformly  distributed. 

Piston  and  Piston  Rings. — In  vertical  steam  engines  there  is  no 
pressure  between  the  cylinder  and  the  cylinder  walls,  except  that 
exerted  by  the  piston  rings.  For  this  reason  the  lubrication  of 
the  pistons  and  piston  rings  in  vertical  engines  is  easier,  and  less 
oil  is  required  than  in  horizontal  engines,  in  which,  besides  the 
pressure  between  the  piston  rings  and  the  cylinder  walls,  is 
frequently  added  the  pressure  of  the  weight  of  the  piston  sliding 
over  the  bottom  of  the  cylinder. 

In  the  case  of  large  horizontal  steam  engines,  the  extra  friction" 
due  to  the  weight  of  the  piston  is  frequently  avoided  by  extending 
the  piston  rod  out  through  the  back  cover  and  connecting  it  to  a 
tail  rod  support.  In  this  way,  by  making  the  piston  rod  suffi- 
ciently rigid,  the  whole  or  part  of  the  weight  of  the  piston  will  be 
supported  by  the  crosshead  and  tail  rod  guides,  so  that  the  duty 
of  the  piston  rings  becomes  only  that  of  preventing  leakage  of 
steam  from  one  side  of  the  piston  to  the  other. 

In  the  case  of  horizontal  steam  engines  employing  highly  super- 
heated steam,  "this  arrangement  will  always  be  found  desirable 
and  frequently  necessary,  as  otherwise  excessive  friction  and  wear 
results. 

The  piston  rings  are  always  softer  than  the  cylinder,  so  that  if 
there  is  any  wear,  the  greatest  wear  will  be  on  the  piston  rings 
and  not  on  the  cylinder  walls. 

During  recent  years  a  number  of  piston  rings  have  been  int.ro- 


STEAM  FATJINTCS  350 

(luced  which  exert  pressure  against  the1  cylinder  walls  due  to  the 
action  of  internal  springs.  Where  the  conditions  are  ideal,  these 
rings  give  good  service,  but  they  are  somewhat  rigid  in  their 
construction,  so  that  where  the  movement  of  the  piston  from  one 
end  of  the  cylinder  to  the  other  is  not  absolutely  central,  experi- 
ence has  proved  that  these  spring  piston  rings  under  extreme 
conditions  have  caused  excessive  friction  and  heavy  wear. 

It  must  be  kept  in  mind  that  the  temperature  of  the  oil  film 
is  high  and  that  excessive  pressure  or  friction  may  easily  destroy 
the  oil  film  and  produce  bad  results.  For  most  conditions  the 
old  Ramsbottom  type  of  split  piston  ring,  which  is  very  flexible, 
therefore  still  holds  its  own  over  a  wide  range  of  service. 

It  is  always  an  advantage  to  have  the  corners  of  the  piston 
rings  rounded  off,  as,  if  they  are  sharp,  they  act  like  scrapers  on 
the  cylinder  walls*  and  destroy  the  oil  film.  When  they  are 
rounded,  they  do  not  dislodge  the  oil  film,  and  better  lubrication 
results. 

The  reason  why  modern  piston-packings  of  rather  complicated 
constructions  are  not  so  widely  used  as  one  might  expect  will 
perhaps  be  found  in  the  fact  that  in  event  of  the  centre  line  of 
the  piston  and  rod  not  being  quite  coincident  with  the  centre 
line  of  the  barrel,  the  flexibility  of  the  piston-packing  may  not 
be  great  enough  to  allow  for  this  difference.  This  has  led  to  an 
endeavor  on  the  part  of  piston-packing  makers  and  designers 
to  embody  in  their  design  the  quality  known  as  "  floating," 
which  means  that  the  particular  type  of  packing  in  use  may  exert 
as  nearly  as  possible  even  pressure  all  round  against  the  walls  of 
the  cylinder,  quite  independently  and  without  affecting  the 
piston  body.  This  same  experience  has  also  led  the  makers  of 
metallic  packing  for  piston  rods,  etc.,  to  allow  the  packing  a 
little  lateral  movement  from  the  rod,  which  prevents  excessive 
friction  and  prevents  distress  of  the  packing  and  subsequent 
blowing. 

Example  27. — The  following  is  an  interesting  example  illustrat- 
ing how  the  various  types  of  piston  packing  may  have  a  bearing 
on  the  lubricating  conditions.  Complaints  were  made  about  a 
cylinder  oil  in  use  on  an  8,000-horsepower,  three-cylinder,  hori- 
zontal rolling  mill  engine,  the  complaint  being  that  excessive 
wear  showed  up  in  the  cylinder,  the  cylinder  walls  appearing 
dry,  no  matter  how  much  oil  was  used. 

The  engine  had  for  several  months  been  running  on  a  very 
small  consumption  of  cylinder  oil  and  giving  every  satisfaction, 
the  oil  being  fed  into  the  three  steam  chests  on  the  cylinders. 
The  engine  was  hardly  powerful  enough  to  cope  with  the  load. 


300  PRACTICE  OF  LUBRICATION 

As  the  chief  engineer  had  a  suspicion  that  some  portion  of  the 
steam  was  leaking  past  the  pistons,  the  cylinders  were  rebored 
and  new  pistons  were  put  in  fitted  with  a  modern  non-floating 
type  of  piston  ring,  instead  of  Ramsbottom  rings  which  were 
employed  previously.  When  the  engine  restarted  it  was  found 
to  be  worse  than  ever,  and  the  output  of  the  steelworks  largeh' 
decreased.  At  the  same  time  the  coal  consumption  went  up, 
and  it  was  quite  apparent  that  more  steam  was  leaking  past  the 
pistons  than  under  the  old  conditions.  The  reason  why  the 
non-floating  rings  did  not  give  satisfaction  was  that  the  axes  of 
the  cylinders  were  not  coincident  with  the  axes  of  the  three  piston 
rods  and  tail  rods.  Accordingly,  the  piston  rings  at  a  certain 
part  of  the  stroke  were  bearing  hard  against  the  cylinder  barrels, 
setting  up  heavy  friction. 

At  the  same  time,  as  the  rings  were  not  moving  freely  enough, 
steam  was  leaking  past  the  pistons  in  enormous  quantities. 
This  will  also  explain  why  the  cylinder  walls  were  dry,  as  the 
steam  oozing  past  the  pistons  would  tend  to  carry  away  the 
film  of  oil  on  the  cylinder  walls.  After  some  experimenting, 
new  sets  of  piston  rings  were  put  in.  These  were  of  a  type 
which  allowed  sufficient  come-and-go  (floating)  to  meet  the 
conditions  of  the  engine.  After  this  satisfactory  results  were 
again  secured  by  the  use  of  the  same  oil,  a  very  marked  im- 
provement being  shown  while  deaUng  with  the  maximum  load, 
and  in  the  coal  bill  falling  to  normal. 

From  the  designer's  point  of  view,  there  are  several  important 
things  to  consider  in  order  to  reduce  the  amount  of  power  con- 
sumed by  friction  in  steam  engine  cylinders. 

Firstly.- — The  weight  of  the  piston  itself  should  preferably  be 
taken  by  means  other  than  the  wearing  surfaces;  in  other  words, 
the  piston  should  not  be  allowed  to  wear  on  the  bottom  of  the  cylinder 
barrel. 

Secondly. — The  duty  of  the  piston  rings  should  be  only  to 
attain  steam-tight  working.  That  construction  would  be  the 
best  which  accomplished  this  with  the  smallest  amount  of  pres- 
sure between  the  piston  rings  and  the  cylinder  walls.  Further, 
the  construction  should  allow  of  a  certain  amount  of  come-and-go, 
as  the  coincidence  of  the  centre  line  of  the  piston  and  that  of  the 
cylinder  barrel  can  never  be  depended  upon  in  actual  practice. 

On  opening  up  steam  cylinders  for  inspection,  the  surface 
should  present  a  rather  dull  apearance,  coated  with  a  thin  film  of 
oil.  The  presence  of  oil  can  be  ascertained  by  striking  a  piece 
of  paper  around  the  cylinder  bore  at  various  parts  of  the  stroke. 
After  the  oil  film  has  been  wiped  off,  the  surface  underneath  should 


STEAM  ENGINES  361 

appear  bright  and  glossy.  If  any  wear  has  taken  place,  the  sur- 
face will  also  be  bright,  but  in  quite  a  different  way,  it  will  look 
silvery  as  if  raw-polished  with  fine  emery  cloth,  and  although 
actual  scoring  may  not  have  taken  place,  there  will  always  be 
found  fine  streaks  indicating  wear.  This  may  be  due  to  a  variety 
of  causes,  such  as  unsuitable  or  improperly  selected  oil;  the  lubri- 
cator may  be  unreliable,  or  the  method  of  lubrication  may  not  be 
satisfactory;  or  possibly,  the  oil  feed  has  been  cut  too  low. 

Packing  Glands. — The  function  of  the  packing  glands  used  for 
piston  and  valve  rods  is  to  prevent  steam  leakage  outward  in 
high  pressure  cylinders,  and  air  leakage  inward  in  low  pressure 
cylinders  of  condensing  engines. 

A  perfect  seal  can  be  obtained  only  by  the  presence  of  a  com- 
plete oil  film  on  the  rods,  so  that  full  and  efficient  lubrication  of 
the  packing  glands  is  essential. 

There  are  many  types  of  piston  rod  glands  in  service,  but  they 
can  be  divided  into  two  main  groups,  viz. :  glands  having  soft 
packing  and  glands  having  metallic  packing. 

Soft  Packing  Glands. — These  are  used  only  under  saturated 
steam  conditions.  The  friction  is  always  comparatively  high,  and 
if  the  packing  is  screwed  up  hard,  undue  pressure  is  produced 
between  the  packing  and  the  piston  rod  which  results  in  scoring 
of  the  latter,  after  which  it  becomes  difficult  to  keep  the  gland 
tight. 

In  reversible  engines  such  as  colliery  winding  engines,  steel 
works  rolling  mill  engines,  etc.,  the  reversing  of  the  engines  takes 
place  by  changing  the  position  of  the  slide  valves  or  piston  valves 
in  relation  to  the  position  of  the  pistons.  This  movement  of  the 
valves  is  done  by  hand  in  the  case  of  small  engines  and  by  a 
special  reversing  engine  in  the  case  of  large  engines.  It  is  obvious 
that  the  pull  required  to  reverse  the  engine  is  influenced  by  the 
frictional  resistance  offered  by  the  valves  moving  on  their  seats, 
and  the  additional  resistance  of  the  valve  rods  moving  in  their 
glands. 

Where  the  valve  rods  have  been  lubricated  externally,  which 
method  is  wasteful  and  inefficient,  a  change  to  the  atomization 
method  of  lubrication  brings  about  a  marked  improvement,  par- 
ticularly moticeable  in  reversible  engines.  The  valve  rods  will 
receive  internal  lubrication  when  inside  the  valve  chest,  and  ac- 
cordingly will  convey  efficient  lubrication  to  the  packing,  so  that 
the  external  lubrication  of  the  valve  rods  can  be  dispensed  with 
altogether. 

The  reversing  lever  will  be  easier  to  operate,  due  to  lower  gland 
friction,  and  this  is  a  point  greatly  appreciated  by  the  engine 


362 


PRACTICE  OF  LUBRICATION 


drivers;  in  fact,  every  change  in  the  grade  of  cylinder  oil  or  in  the 
method  of  application  will  be  immediately  noticed  in  the  pull 
required  to  shift  the  reversing  lever. 

Metallic  Packing  Glands. — Fig.  153  shows  a  simple  design. 
Metallic  packing  is  superior  to  soft  packing.  The  gland  fric- 
tion with  metallic  packing  is  appreciably  less  than  with 
soft  packing  and  there  is  much  less  danger  of  scoring  taking 
place. 

It  is  essential  when  using  metallic  packing  that  the  deflection 
and  movement  of  the  piston  rod  can  take  place  without  setting- 
up  any  undue  pressures  in  the  packing,  which  should  exert  only 
a  slight  pressure  against  the  piston  rod.  This  is  accomplished  by 
ball  joints  and  annular  " floating  spaces"  round  the  packing. 


FIG.   153. — Metallic  packing. 

Metallic  packing  is  always  employed  in  the  case  of  superheated 
steam  and  also  in  the  case  of  high  pressure  saturated  steam  in 
large  engines. 

When  the  atomization  method  of  lubrication  is  employed  with 
saturated  or , moderately  superheated  steam,  it  is  frequently  un- 
necessary to  lubricate  the  metallic  packing  direct.  In  the  case 
of  highly  superheated  steam,  however,  it  is  always  necessary  to 
have  a  direct  feed  of  cylinder  oil  into  the  metallic  packing.  Only 
the  highest  grade  of  cylinder  oil  should  be  used  for  this  purpose 
and  should  be  fed  uniformly  and  sparingly,  as  the  excess  oil  re- 
mains stagnant  in  the  casing,  which  holds  the  packing,  and  being 
exposed  to  high  temperature  the  oil  is  inclined  to  bake  into  car- 
bonaceous deposits. 


STEAM  ENGINES  363 

DEPOSITS 

Experience  shows  that  in  most  cases  where  deposits  develop  in 
steam  engines,  the  cause  can  be  traced-back  to  the  boiler  conditions. 
The  deposit,  if  analyzed,  will  usually  prove  to  be  ''boiler  matters" 
amalgamated  with  a  greater  or  less  percentage  of  cylinder  oil, 
decomposed  oil,  iron  and  oxides  of  iron. 

Deposits  Due  to  'Dirty  Feed  Wacer. — Where  the  feed  water  is 
taken  from'  rivers,  it  should  be  taken  from  as  clean  a  place  as 
possible  and  impurities  should  be  prevented  from  entering  the 
water  supply.  In  rainy  weather  the  rivers  are  swollen  and 
muddy,  and  if  dirty  feed  water  is  introduced  into  the  boilers 
they  are  apt  to  prime,  and  the  impurities  will  be  carried  over 
with  the  steam  and  cause  deposits. 

In  India  the  river  water  contains  some  very  fine  suspended 
matter;  this  silt  gets  carried  over  with  the  steam  when  the  boilers 
prime  and  causes  deposits  inside  the  engines.  It  will  appear  that 
heavily  compounded  oils  have  proved  successful  in  preventing 
such  deposit  from  caking  and  hardening,  whereas  with  mineral 
or  only  slightly  compounded  oils  the  deposit  becomes  hard  and 
very  troublesome. 

Example  28. — A  500-horsepower,  horizontal,  tandem,  com- 
pound steam  engine,  using  slightly  superheated  steam,  had  been 
lubricated  satisfactorily  with  a  good  grade  of  dark  cylinder  oil. 
After  an  economizer  breakdown,  trouble  immediately  started  and 
a  black  deposit  developed  in  the  cylinders.  The  analysis  was  as 
follows : 

Water 6.0  per  cent. 

Oil  and  volatile  matter 43.4  per  .cent. 

Metallic   iron,   oxides  of  iron,   lime  and 

traces  of  copper 50. 6  per  cent. 

It  was  found  that  the  feed  water  was  of  very  poor  quality  and 
contained  a  large  quantity  of  impurities.  However,  as  it  passed 
the  Green's  economizer  before  it  entered  the  boilers,  the  economizer 
pipes  had  the  effect  of  precipitating  the  impurities  in  the  lower 
bends  and  the  feed  water  was  pumped  into  the  boilers  almost 
clean.  A  sample  of  impurities  taken  from  one  of  the  lower  -bends 
of  the  economizer  piping  was  analyzed  and  showed  a  composition  of 
oxides  of  iron,  with  a  large  percentage  of  carbonate  of  lime,  sili- 
cates, and  also  traces  of  coal  ash. 

When  the  economizer  broke  down,  the  impure  feed  water  was 
pumped  direct  into  the  boilers,  and  on  the  boilers  priming,  the 


364  PRACTICE  OF  LUBRICATION 

steam  carried  the  impurities  over  into  the  steam  engine,  which 
explains  the  trouble. 

While  on  the  subject  of  superheated  steam,  it  may  not  be  out  of 
place  to  mention  the  necessity  for  good  control  of  the  temperature 
of  the  steam. 

Example  29. — In  one  case  trouble  was  experienced  in  a  steam 
engine  employing  superheated  steam,  although  the  temperature 
of  superheat,  as  indicated  by  the  thermometer  placed  jusl  in 
front  of  the  engine  stop  valve,  only  showed  530°F. 

When  another  thermometer  was  brought  along  it  recorded  a 
temperature  120  degrees  in  excess  of  this,  showing  that  the  old 
thermometer,  probably  on  account  of  the  superheat  on  occasions 
exceeding  the  normal,  had  been  overheated.  Such  overheating  will 
always  produce  a  weakening  of  the  bulb  which  means  a  lowering 
of  the  mercury  in  the  stem,  and  the  thermometer  therefore  reads  too 
low. 

Where  a  steam  trap  is  not  fitted  or  is  of  insufficient  capacity, 
the  boiler  sludge  will  deposit  in  the  corners  and  cavities  of  the 
valve  chest,  in  the  clearance  spaces  of  the  cylinder,  behind  the 
piston  rings,  etc.  Where  the  oil  is  introduced  into  the  main 
steam  pipe  and  finely  atomized,  the  greater  part  of  the  boiler 
sludge  will  be  swept  through  the  engine  and  the  valve  chambers, 
cylinders,  etc.,  will  keep  cleaner  than  where  cylinder  oil  is  applied 
direct. 

The  following  example  shows  the  importance  of  fitting  a  steam 
separator. 

Example  30. — An  oil  of  good  quality  had  been  used  on  a  steam 
engine  employing  superheated  steam  and  giving  every  satis- 
faction. Without  warning,  trouble  began.  The  oil  carbonized 
in  the  cylinders  and  heavy  wear  of  the  internal  surfaces  was 
noticed.  A  sample  of  the  black  deposit  was  analyzed,  and  con- 
tained the  following  constituents: 

Traces  of  lime  (carried  over  from  the  boilers.) 

56.4  per  cent,  metallic  iron  and  oxides  of  iron,  principally  metallic 

iron,  produced  by  wear. 
12.8  per  cent,  free  oil. 
30.8  per  cent,  volatile  matter,  chiefly  carbonized  oil. 

It  was  found  that  through  an  alteration  in  the  pipe  line  some 
borings  had  dropped  into  the  steam  line,  and  were  urged  along 
with  the  steam.  The  trouble  continued  for  a  considerable  length 
of  time,  until  the  last  boring  had  disappeared.  Afterward  no 
trouble  was  experienced,  the  same  oil  giving  the  satisfaction  it 
gave  before. 


STEAM  ENGINES  365 

Deposits  Due  to  Impurities  in  the  Steam. — The  solid  impurities 
in  the  steam  are  mainly  two  kinds,  namely: 

1.  Iron  oxides  (rust)  from  the  boiler,  the  superheater  tubes,  or 
from  the  steam  line. 

2.  Boiler  salts  and  boiler  impurities  carried  over  with  the 
steam  during  periods  of  priming. 

Rusty  scale  may  come  from  the  superheater  tubes  and  the 
steam  pipe.  The  cast-iron  or  steel  surfaces  in  the  tubes  or  pipes 
will  in  time  be  covered  by  a  rusty  scale  produced  by  oxidation, 
as  there  is  always  a  slight  percentage  of  air  mixed  with  the  steam. 
Owing  to  the  vibration  of  the  steam  pipes  and  to  the  expansion 
and  contraction  due  to  the  temperature  variations,  this  rust  in 
time  breaks  loose,  and  is  carried  into  the  engines.  The  iron 
oxides  from  the  superheaters  is  often  in  the  form  of  a  very  fine 
black  dust  whereas  the  rust  from  the  steam  pipe  is  more  coarse. 
The  impurities,  whatever  kind  they  may  be,  when  entering  the 
steam  engine  adhere  and  cling  to  the  oil  film  all  over  the  internal 
rubbing  surfaces.  The  result  is  the  formation  of  a  dark  colored 
sludge  or  paste,  which  accumulates  in  the  valves,  valve  ports  and 
passages,  the  spaces  between  and  behind  the  piston  rings  and  on 
the  piston  faces. 

In  extreme  cases  the  piston  rings  will  be  completely  choked 
with  deposits;  they  become  inflexible  in  their  grooves;  they  no 
longer  perform  their  duty  of  preventing  leakage  of  steam  from 
one  side  of  the  piston  to  the  other,  and  the  result  is  excessive 
wear  of  the  piston  rings  and  the  cylinder,  also  heavy  loss  in  power 
due  to  the  increased  friction  and  steam  leakage  past  the  piston. 
The  valves  and  pistons  groan,  and  the  various  indications  of 
excessive  friction  characteristic  of  the  different  kinds  of  valve 
motion  will  become  apparent. 

When  using  saturated  steam,  and  particularly  wet  saturated 
steam,  the  washing  effect  of  the  wet  steam  has  a  tendency  to 
remove  the  deposits  from  the  high  pressure  cylinder  and  valves, 
but  they  are  then  frequently  found  in  the  passages  leading  from 
the  high  pressure  cylinder  to  the  low  pressure  cylinder,  or  in  the 
latter. 

Sometimes  a  liberal  supply  of  oil  or  the  use  of  a  light  bodied 
compounded  cylinder  oil  will  temporarily  relieve  the  distress  of 
the  engine. 

In  the  case  of  superheated  steam,  the  deposits  formed  in  the 
high  pressure  valves,  valve  chambers  and  cylinders,  particularly 
when  very  heavy  viscosity  dark  cylinder  oils  are  used,  remain  there 
and  are  baked  into  hard,  carbonaceous  deposits,  which  are  most 
objectionable  and  cause  heavy  wear.  A  liberal  oil  feed  will  only 


366  PRACTICE  OF  LUBRICATION 

accentuate  this  trouble,  as  the  excess  oil  simply  decomposes  and 
forms  more  deposits.  The  use  of  a  light  bodied  compounded 
filtered  cylinder  oil  will  frequently  help  to  loosen  the  deposits  and 
remove  them  from  the  high  pressure  valves  and  cylinders. 

In  many  cases  where  heavy  carbonization  has  been  experienced, 
great  improvements  have  been  brought  about  by  introducing  the 
atomization  method  of  lubrication.  It  is  obvious  that,  where  oil 
is  introduced  direct  to  the  various  frictional  surfaces,  it  takes 
time  for  it  to  spread;  therefore  more  oil  is  required  and  it  is  to 
this  surplus  oil  that  the  impurities  particularly  adhere.  Where 
the  cylinder  oil  is  thoroughly  atomized  with  the  steam,  it  is 
spread  to  the  best  advantage  over  the  internal  surfaces;  it 
presents  only  a  thin  lubricating  film,  and  there  is  no  surplus  oil 
to  which  the  impurities  can  adhere.  Better  atomization  and 
distribution  of  the  cylinder  oil  results  therefore  not  only  in  greater 
economy,  but  also  means  cleaner  lubrication  internally,  that  is, 
less  formation  of  deposits. 

Where  the  steam  is  very  pure,  carbonization  seldom  occurs 
when  good  quality  oils  are  used,  not  even  if  the  oils  are  fed  direct 
and  not  atomized.  If,  however,  the  steam  is  dirty,  the  impurities 
adhere  to  the  oil  film,  and,  due  to  the  high  temperature,  a  layer 
of  oil  carbon  will  be  formed  by  oxidation.  Later,  a  new  layer  of 
impurites  will  cover  the  layer  of  oil  carbon,  and  another  layer  of 
oil  will  produce  more  oil  carbon,  so  that  if  a  crust  of  carbonaceous 
matter  is  examined  it  will  frequently  be  seen  to  consist  of  alter- 
nate layers  of  impurities  and.  oil  carbon. 

Compounded  filtered  cylinder  oils  of  good  quality  will  produce 
practically  clean  lubrication,  notwithstanding  dirty  steam;  such 
oils  prevent  the  impurities  from  caking  together  with  the  oil,  so 
that  they  are  swept  out  of  the  cylinder  with  the  steam. 

Where  the  feed  water  is  treated  chemically  and  where  a  surplus 
of  soda  reaches  the  boiler  and  priming  occurs,  even  a  small 
quantity  of  soda  in  the  steam  will  have  a  very  deleterious  effect  on 
lubrication.  The  soda  dries  up  the  oil  film  and  a  more  liberal  oil 
feed  is  required  when  using  saturated  steam,  whereas  in  the  case 
of  superheated  steam  a  greater  feed  of  oil  will  usually  mean  more 
trouble  and  increased  formation  of  carbonaceous  deposits. 

When  reheaters  are  installed  between  the  high  pressure  and 
lower  stage  cylinders,  the  oil  may  be  carbonized  in  these  re- 
heaters  and  if  some  of  it  is  carried  over  it  will  cause  deposits  in 
the  intermediate  or  low  pressure  cylinders. 

Example  31. — The  following  analysis  of  a  deposit  taken  from 
the  valve  chest  of  a  1000-horsepower  horizontal  steam  engine  is 
typical  of  deposits  due  to  priming  of  boilers. 


STEAM  ENGINES  367 

Iron  and  iron  oxides 2.3  per  cent. 

(This  represents  slight  wear  of  the  inter- 
nal surfaces  and  rust  carried  to  the 
engine  from  the  steam  line.) 

Carbonate  of  soda,  caustic  soda  and  car- 
bonate of  lime 44 . 2  per  cent. 

(This  has  come  from  the  boiler.) 

Oil  and  volatile  matter,  chiefly  oil 49.2  per  cent 

Water 4.3  per  cent. 

Example  32. — On  a  colliery  where  the  water  used  for  boiler 
purposes  was  hard,  the  practice  was  to  introduce  soda  direct  into 
the  boilers.  Owing  to  this,  and  also  to  the  fact  that  the  boilers 
were  worked  rather  at  overcapacity,  priming  frequently  occurred. 
It  was  found  that  when  the  steam  was  very  wet  and  carried 
water  containing  boiler  solids  in  suspension  and  various  soluble 
salts,  all  these  solids  deposited  themselves  in  the  bottom  bends  of 
the  superheater  tubes,  the  water  evaporating.  When  priming 
of  the  boilers  ceased,  the  steam  going  through  the  superheaters 
carried  the  dry  dust  in  the  bottom  bends  into  the  steam  engines, 
where  the  deposits  had  the  effect  of  " drying  up"  the  oil  film,  so 
that  the  piston  rods  appeared  dry;  groaning  of  valves  and  pistons 
was  noticed,  and  could  be  stopped  only  with  a  very  copious  supply 
of  cylinder  oil.  The  cylinder  oil  was  introduced  into  the  main 
steam  pipe  through  atomizers.  Due  to  this,  quite  a  large  per- 
centage of  the  deposit  was  swept  through  the  engine  with  the 
exhaust  steam  and  into  an  exhaust  steam  turbine.  The  oil 
and  the  boiler  solids  deposited  themselves  on  the  turbine  blades 
and  necessitated  frequent  cleaning,  at  the  same  time  decreasing 
the  efficiency  considerably. 

When  a  feed  water  softening  plant  was  installed  the  priming 
of  the  boilers  was  entirely  overcome  and  the  troubles  ceased. 

A  chemical  analysis  of  deposits  developed  in  steam  engines  will, 
as  indicated  in  the  examples,  always  be  of  service  in  tracing 
their  cause.  A  very  simple  test  which  can  easily  be  carried  out  is 
to  take  a  portion  of  the  deposit  and  burn  it  on  a  hot  plate.  The 
oil  will  burn  away,  and  the  residue,  if  consisting  mainly  of  iron 
and  rust,  will  indicate  that  rusty  matters  have  been  carried  over 
to  the  engine  or  that  wear  is  taking  place;  if  the  residue  consists 
of  chalky  matters  of  a  light  color,  or  of  a  yellowish  reddish  color, 
it  indicates  priming  of  the  boilers,  the  boiler  salts  being  carried 
over  with  the  steam  into  the  engine.  If  the  whole  of  the  deposit 
burns  away,  it  shows  that  the  oil  in  use  has  produced  oil  carbon, 
and  that  either  it  is  an  unsuitable  quality  of  oil,  or  the  oil  is  used 
in  excess  or  is  not  distributed  in  the  best  possible  manner. 

To  avoid  priming  it  is  important  that  the  feed  water  softening 


368 


PRACTICE  OF  LUBRICATION 


plant  shall  be  in  good  working  order  and  that  the  tendency  of 
the  boiler  to  prime  be  overcome  or  minimized  by  keeping  a  proper 
water  level,  by  keeping  the  water  in  the  boiler  in  good  condition, 
and  having  sufficient  boiler  capacity,  so  that  the  boilers  are  not 
overloaded. 


LUBRICATION  OF  CORLISS  VALVE  ENGINES 

In  the  following  the  lubrication  of  Corliss  valves  will  be  briefly 
analyzed. 

Fig.  154A  and  B  illustrate  the  high  pressure  cylinder  of  a 
steam  engine  having  Corliss  valves.  The  piston  (1)  is  shown  in 


A  B 

FIG.   154. — Corliss  valve  lubrication. 

Fig.  154 A  as  moving  toward  the  left,  the  steam  being  exhausted 
through  the  exhaust  valve  (2)  to  the  exhaust  pipe  (3)  leading  to 
the  low  pressure  cylinder  (possibly  through  a  receiver).  The 
steam  coming  from  the  steam  pipe  (4)  into  the  valve  chest  (5) 
enters  the  cylinder,  alternately  passing  the  admission  valve  6a 
or  66. 

Fig.  154B  shows  a  cross  section  of  the  cylinder  and  the  valves. 
The  admission  valve  (66)  is  operated  through  the  spindle  (7)  by 
means  of -the  lever  (8).  The  valve  will  require  lubrication  on  the 
entire  surface  in  contact  with  the  valve  face.  How  is  this  best 
accomplished? 


STEAM  ENGINES  369 

The  first  attempt  made  to  lubricate  a  valve  of  this  description 
was  by  feeding  the  oil  direct  into  the  centre  of  the  valve,  as  shown 
by  (9)  in  Fig.  1545.  What  happened,  however,  was  this:  the 
oil  which  dropped  on  to  the  centre  of  the  valve  was  immediately 
swept  through  the  valve  port  opening.  Although  the  valve 
needed  to  be  lubricated  along  its  entire  length,  the  oil  was  not 
given  a  chance  to  do  so,  and  only  succeeded  in  lubricating  a 
narrow  strip  of  the  valve  and  valve  face  just  in  the  centre. 

A  slight  improvement  on  this  system  is  feeding  the  oil  at  the 
points  10  and  11  instead  of  feeding  it  at  the  centre.  But  in  this 
case  also  the  steam  will  sweep  the  drops  of  oil  through  the  valve 
ports  and  prevent  the  oil  from  spreading  over  the  entire  valve 
face.  The  system  is  therefore  not  by  a  long  way  satisfactory, 
although  it  is  advocated  by  the  majority  of  engine  builders. 

Where,  however,  Corliss  valves  are  very  big,  or  where  the  steam 
is  not  very  clean,  or  in  cases  of  superheated  steam,  all  sorts  of 
difficulties  and  trouble  may  occur.  The  valves  groan  and  wear. 
They  may  even  stick,  refusing  to  move,  causing  serious  irregu- 
larities in  the  working  of  the  engine.  The  cause  of  the  trouble  is 
bad  lubrication,  particularly  of  the  two  ends  of  the  valves,  the 
valve  end  rubbing  hard  against  the  end  cover.  It  is  quite  evi- 
dent that  if  it  be  difficult  for  the  oil  to  remain  on  the  middle  part 
of  the  valve,  it  will  be  even  more  difficult  for  it  to  reach  the  two 
ends  of  the  valves, where  the  oil  is  most  neecled. 

Probably  steam  will  constantly  keep  condensing  and  will  reach 
the  valve  ends,  but  will  tend  only  to  wash  away  any  oil  that  may 
be  present,  except  when  the  steam  itself  has  been  thoroughly 
lubricated,  and  therefore  practically  becomes  a  lubricant.  In 
order  to  get  the  best  results  the  steam  must  be  lubricated.  In  the 
illustration,  a  double  feed  mechanical  lubricator  (12)  is  mounted 
on  the  engine,  actuated  by  some  part  of  the  valve  mechanism, 
and  discharging  cylinder  oil  through  pipe  13  leading  to  the  check 
valve  14,  the  drops  of  oil  trickling  down  inside  the  atomizer  15 
being  exposed  to  the  central  flow  of  steam. 

In  this  way  every  drop  of  oil  will  be  divided  into  thousands  of 
the  most  minute  particles,  and  will  be  intimately  mixed  with 
the  steam,  so  that  when  the  steam  is  admitted  through  the  admis- 
sion valve  (6a)  or  (66)  it  sweeps  over  the  valve  faces  and  seats 
and  will  deposit  sufficient  oil  to  lubricate  thoroughly.  Further, 
some  of  the  oily  steam  will  condense  and  carry  oil  to  both  ends 
of  the  valves  and  to  the  valve  end  rubbing  against  the  valve 
cover.  Oil  pipe  (16)  carries  oil  to  the  low  pressure  cylinder. 

Cases  have  been  known  where  it  was  impossible  to  stop  the 
groaning  of  a  Corliss  valve  even  with  a  feed  of  120  drops  per 

24 


370  PRACTICE  OF  LUBRICATION 

minute  of  good  cylinder  oil,  and  where  the  mere  change  of  the 
oil  feed  from  feeding  " direct"  on  to  the  valve  to  feeding  into  the 
steam  pipe  had  an  almost  immediate  effect  of  silencing  the  valve, 
and  doing  this  on  a  consumption  of  between  one  and  two  drops 
per  minute.  It  is  the  old  story  over  again,  that  "a  drop  of  oil  in 
the  right  place  is  better  than  a  gallon  on  the  floor." 

If  the  steam  has  free  access  to  one  end  of  the  valve,  and  the 
access  to  the  other  end  is  restricted,  wobbling  of  exhaust  valves 
may  occur  at  each  stroke  of  the  engine.  The  cause  for  this  will 
be  readily  understood. 

Knocking  of  the  valve  operating  motions  may  be  due  to  im- 
proper lubrication  of  the  valves,  but  may  also  simply  be  produced 
by  a  loose  joint  somewhere.  This  can  easily  be  detected  by 
flooding  one  bearing  after  another  of  the  external  motion  with 
oil.  When  the  bearing  which  caused  the  knocking  is  excessively 
lubricated  in  this  way,  the  knock,  which  ordinarily  is  sharp,  will 
be  deadened  as  the  thicker  oil  film  in  the  bearing  will  cushion  the 
blow.  Adjustment  of  the  bearing  in  question  should  therefore 
generally  overcome  the  trouble. 

LUBRICATION  OF  COLLIERY  WINDING  ENGINES 

The  lubrication  of  colliery  winding  (hoisting)  engines  presents 
several  interesting  features.  Many  winding  engines  are  inter- 
nally lubricated  by  means  of  hydrostatic  sight-feed  lubricators 
feeding  the  cylinder  oil  either  into  the  valve  chest  or  valves,  or 
into  the  main  steam  pipe.  Winding  engines  are  generally  hori- 
zontal twin  steam  engines,  the  main  steam  pipe  branching  off  to 
each  engine,  and  usually  a  sight-feed  lubricator  is  mounted  on 
each  branch  pipe  between  the  throttle  valve  and  its  respective 
engine.  As  winding  engines  work  intermittently,  it  will  be 
understood  that  when  sight  feed  lubricators  are  in  use  a  good 
portion  of  the  cylinder  oil  will  be  wasted,  as  they  continue  to  deliver 
oil  during  the  periods  when  the  engine  is  standing.  As  the  sight- 
feed  lubricators  are  generally  mounted  between  the  throttle 
valve  and  the  engine,  it  will  in  such  cases  be  found  difficult  to 
operate  the  throttle  valve,  and  the  valve  stem  will  be  found  subject 
to  more  or  less  wear  owing  to  lack  of  lubrication. 

Hydrostatic  lubricators  are  seldom  equipped  with  atomizers,  so 
that  the  drivers  of  winding  engines  generally  complain  of  diffi- 
culty in  operating  the  reversing  lever,  owing  to  heavy  friction 
in  the  valves  and  glands. 

It  will  also  be  found  that  in  order  to  minimize  wear  on  the  valve 
stems  and  piston  rods  it  becomes  necessary  to  swab  the  rods  or  to 


STEAM  -ENGINES 


371 


lubricate  them  through  a  sight-feed  drop  oiler,  dropping  cylinder 
oil  on  the  rods  outside  the  glands.  This  is,  of  course,  very 
wasteful,  as  most  of  the  oil  is  scraped  off  the  glands  and  runs  to 
waste. 

When  a  mechanical  lubricator  is  used  feeding  the  oil  into  the 
main  steam  pipe  before  the  throttle  valve,  through  an  atomizer, 
one  oil  feed  will  do  to  supply  all  requirements  for  the  internal 
lubrication  of  throttle  valve,  reversing  engine  and  two  cylinders, 
if  the  steam  pipe  comes  to  each  cylinder  by  an  equal  branch  as 
in  Fig.  155A,  in  which  (1)  is  the  lubricator  feeding  cylinder  oil 
into  steam  pipe  at  (2).  But  two  feeds  are  necessary  if  the  steam 
pipe  is  arranged  as  in  Fig.  155B,  for  the  greater  inertia  and  density 
of  the  cylinder  oil  compared  with  that  of  the  steam  carries  it  past 
the  branch  pipe  4  of  the  near  cylinder,  most  of  the  oil  being  car- 
ried to  the  right-hand  engine. 


A  B 

FIG.   155. — Lubrication  of  colliery  hoisting  engines. 

Ordinarily,  therefore,  a  two-feed  lubricator  should  be  fitted, 
feeding  into  the  branches  (4)  and  (5)  respectively  at  the  points 
(2)  and  (3). 

If  it  be  considered  necessary  to  lubricate  the  throttle  valve  (6) 
automatically,  an  extra  feed  can,  of  course,  be  put  in  to  deal  with 
the  throttle  valve  at  (7) ;  but  if  this  valve  is  of  the  equilibrium 
type,  a  swab  with  cylinder  oil  on  the  valve  rod  at  week-ends  will 
suffice  to  keep  gland  and  valve  stem  in  good  order. 

The  advantages  resulting  from  this  manner  of  applying  the 
right  grade  of  cylinder  oil  are  many. 

First. — There  is  no  waste  of  oil,  as  it  is  fed  into  the  main  steam 
pipe  in  direct  proportion  to  the  number  of  revolutions  made  by 
the  engine.  The  lubricator  stops  feeding  when  the  engine  comes 
to  rest. 


372  PRACTICE  OF  LUBRICATION 

Second. — As  the  oil  is  properly  atomized  and  distributed 
throughout  the  body  of  the  steam,  the  main  stop  valve  and  the 
throttle  valve  will  be  lubricated,  and  therefore  easier  to  handle, 
the  wear  will  be  overcome  and  the  reversing  engine  will  need  no 
separate  lubrication. 

Third. — Each  engine  will  receive  its  portion  of  the  oil  required 
for  satisfactory  lubrication  and  it  will  be  found  unnecessary  to 
use  the  tallow  cups  which  are  often  used  to  give  an  extra  dose  of 
cylinder  oil  direct  into  the  cylinders  when  the  oil  is  not  properly 
atomized. 

Fourth. — As  the  steam  is  thorough^  lubricated,  the  valve  rods 
and  piston  rods  when  coming  inside  the  steam  chest  or  cylinder 
will  be  coated  with  a  good  film  of  oil,  and  thus  receive  their  share 
of  lubrication,  which  in  turn  will  mean  better  lubrication  of  the 
gland  packing,  whether  metallic  or  soft.  Accordingly,  less  wear 
of  the  piston  and  valve  rods  will  be  apparent  and  the  packing  will 
have  a  longer  life.  It  will  generally  be  found  unnecessary  to 
apply  cylinder  oil  externally  to  the  rods. 

Fifth. — Owing  to  the  better  lubrication  of  the  valve  glands  and 
of  the  valves,  the  reversing  lever  will  be  easier  to  operate;  and 
this  is  a  point  greatly  appreciated  by  drivers  of  winding  engines. 

Sixth. — Owing  to  the  better  lubrication,  which  means  less 
power  consumed  in  overcoming  the  friction,  the  engine  -drivers 
find  that  they  can  shut  off  steam  earlier  when  the  cage  is  nearing 
the  end  of  its  journey,  and  they  also  find  that  they  can  acceler- 
ate the  engines  and  the  cage  more  quickly,  or  with  less  opening 
of  the  throttle  valve. 

Much  the  same  remarks  apply  to  steel-works  rolling  mill  en- 
gines, which  also  work  intermittently,  and  usually  are  reversing. 

UNIFLOW  STEAM  ENGINES  (STUMPF  ENGINES) 

The  Stumpf  engine  has  one  cylinder  only;  steam  of  high  pres- 
sure and  high  superheat  expands  right  down  to  the  condenser 
vacuum,  the  exhaust  taking  place  through  the  piston  uncovering 
exhaust  port  in  the  centre  of  the  cylinder. 

There  are  thus  no  exhaust  valves;  the  piston  is  very  long,  so  that 
the  exhaust  ports  are  uncovered  only  at  the  right  moments.  After 
the  steam  has  been  exhausted  and  the  piston  moves  back  it  com- 
presses the  remaining  steam  and  the  clearance  space  when  the 
piston  is  at  the  end  of  its  stroke  is  very  small,  the  intention  being 
that  the  compression  should  rise  quite  up  to  the  boiler  pressure. 

As  the  steam  always  exhausts  through  ports  in  the  centre  of 
the  cylinder  and  always  enters  at  each  end  alternatively  of  the 
cylinder,  the  temperature  of  the  cylinder  ends  will  be  very  high, 


STEAM  ENGINES  373 

;ind  the  temperature  in  the  centre  very  low,  the  steam  always 
flowing  in  the  same  direction;  hence  the  name  Uniflow  Engines, 
as  they  are  often  called. 

The  Stumpf  engine  will  give  the  same  efficiency  as  an  ordinary 
compound  engine  using  superheated  steam. 

Owing  to  the  small  clearance  great  accuracy  is  necessary  in 
manufacture  and  adjustment,  and  the  valves  must  not  leak. 

The  diagram  Fig.  156  is  taken  from  a  uniflow  engine  suffering 
from  two  faults,  namely,  too  small  clearance  (at  that  end  of  the 
cylinder)  and  leakage  through  the  admission  valve.  It  will  be 
seen  that  the  piston  during  the  compression  stroke  compresses 
the  steam  that  leaks  in  to  a  point  far  above  the  boiler  pressure, 
partly  due  to  the  clearance  space  being  smaller  than  intended. 
The  effect  of  this  high  compression  is  that  the  steam  in  the  com- 
pression space  is  heated  far  above  the 
normal  temperature;  it  may  reach  as  3 
high  as  700°F.  which  has  a  very  bad  1 
effect  on  the  piston  rod  and  the  metallic 
packing.  The  piston  rod  may  become 
so  hot  that  the  oil  fumes  and  carbon-  2 
izes  badly/ 

rrn        i  ,  i       i    „        i    i     •  ,1  FIG.    156. — Faulty    uniflow 

The  best  method  to  lubricate  the  engine  diagram,  i.  Boiler 
Stumpf  engine  is  by  a  six-feed  mechan-  pressure.  2.  Atmospheric  line. 

11  111-  T   ,    -i  3.       Maximum      compression 

ically  operated  lubricator,  distributing  pressure. 
the  oil  feeds  as'  follows : 

1.  One  feed  into  steam  main  before  the  stop  valve,  feeding 
through  an  atomizer. 

2-3.  Two  feeds,  one  into  each  of  the  vertical  steam  pipes,  also 
through  atomizers. 

4-5.  Two  feeds,  one  into  each  of  the  admission  valves,  as  on 
light  load  the  oil  fed  into  the  steam  pipes  will  not  be  atomized  and 
reach  the  cylinder  in  sufficient  quantity. 

6.  One  feed  into  the  metallic  packing  of  the  piston  rod. 

As  these  engines  run  at  a  high  speed  the  oil  from  the  crosshead 
is  likely  to  be  splashed  on  the  piston  rod  and  get  carried  into  the 
packing  where  it  carbonizes.  It  is,  therefore,  always  advisable 
to  use  cylinder  oil  for  lubrication  of  the  crosshead  and  sometimes 
also  for  the  guides,  unless  special  precautions  are  taken  for  pre- 
venting the  bearing  oil  from  getting  on  to  the  piston  rod.  (See 
Fig.  90,  page  247.) 

MARINE  STEAM  ENGINES 

Marine  steam  engines  are  often  poorly  lubricated.  This  is 
because  in  times  gone  by  disastrous  accidents  and  troubles  with 


374  PRACTICE  OF  LUBRICATION 

boilers  have  occurred  due  to  the  cylinder  oil  used  for  internal 
lubrication  being  carried  into  the  boilers.  InsteacUrf  endeavor- 
ing to  obtain  full  lubrication  and  yet  avoid  boiler  troubles, 
marine  engineers  have  gone  to  the  other  extreme  and  have,  except 
in  the  case  of  engines  employing  superheated  steam,  confined 
themselves  to  swabbing  the  piston  rods  and  valve  rods  only, 
with  a  liberal  supply  of  cylinder  oil  through  the  tallow  cups, 
when  acute  trouble  made  it  necessary  to  apply  this  remedy. 

By  the  well-known  practice  of  " swabbing  the  rods"  most  of 
the  cylinder  oil  is  scraped  off  by  the  glands  and  runs  to  waste 
and  only  very  little  oil  gets  past  the  packings  inside  the  engine, 
with  the  result  that  at  best  only  the  lower  parts  of  valve  chambers 
and  cylinders  are  lubricated,  and  only  very  inefficiently. 

Usually,  the  swab-pot  has  an  open  top  and  is  exposed  to 
coal  dust,  dirt  and  impurities,  which  may  well  give  rise  to 
trouble. 

The  virtue  of  well  lubricated  valves  and  pistons  is  not  only 
that  the  frictional  losses  are  reduced,  but  also  that  an  oil  seal 
is  provided  on  the  rubbing  surfaces,  which  prevents  or  mini- 
mizes leakage  of  steam  past  the  valves  and  pistons. 

Marine  engines  employing  superheated  steam  cannot  operate 
without  lubrication.  Mechanically  operated  lubricators  are 
provided,  which  feed  the  oil  into  the  main  steam  pipe  or  direct 
to  the  valves,  cylinders  and  packings,  and  if  proper  care  be  taken 
in  selecting  the  correct  quality  of  oil  and  in  extracting  the  oil 
from  the  exhaust  steam  before  it  reaches  the  boilers,  complete 
and  efficient  lubrication  can  be  obtained  without  any  danger  of 
boiler  troubles. 

It  would  be  desirable  to  employ  this  same  system  for  marine 
engines  using  saturated  steam.  The  quantity  of  oil  required  is 
very  small  indeed  and  the  best  results  are  certainly  obtained  by 
feeding  a  minimum  quantity  of  the  correct  grade  of  oil  into  the 
main  steam  pipe  before  the  engine  stop  valve,  feeding  the  oil 
with  such  regularity  as  will  ensure  an  unbroken  oil  film  between 
the  frictional  surfaces. 

Extraction  of  Oil  Exhaust  Steam  Oil  Separator. —  Whereas 
exhaust  steam  oil  separators  for  a  long  time  have  been  in  very 
general  use  on  steam  engine  plants  ashore,  they  have  not  yet 
gained  the  same  universal  favor  among  marine  engineers. 
Exhaust  steam  oil  separators  have,  however,  been  designed  which 
are  compact  and  suitable  for  marine  service. 

If  the  bulk  of  the  oil  from  the  exhaust  steam  is  removed  by 
means  of  an  oil  separator,  the  result  is  that  practically  no  oil  is 
left  in  the  steam  to  settle  on  the  condenser  tubes;  this  is  a  great 


STEAM  ENGINES  375 

advantage,  as  oily  deposits  in  the  condenser  greatly  impair  its 
efficiency.  It  also  means  that  the  oil  filters  will  more  easily 
take  care  of  the  remainder  of  the  oil  and  will  not  need  cleaning 
so  often. 

Where  the  internal  surfaces  are  well  worn  together  and  a  good 
skin  produced,  it  is  sometimes  possible,  witnout  any  apparent 
inconvenience  or  trouble  (owing  to  the  wet  steam  generally 
carried)  to  operate  marine  steam  engines  for  long  periods  without 
internal  lubrication;  but  the  internal  friction  is  considerably 
higher  than  when  proper  lubrication  is  employed,  and  the  wear 
produced  on  the  piston  rings  often  makes  itself  apparent  by  pro- 
ducing sharp  edges,  so  that  the  rings  act  as  scrapers  on  the  cylinder 
walls,  producing  heavy  wear  all  round.  Further,  when  no  oil  is 
used  internally,  the  leakage  of  steam  past  the  piston  rings  is  often 
considerable. 

Example  33. — A  remarkable  instance  was  reported  in  " Power," 
for  July  21,  1908.  Four  first-class  armored  cruisers  of  the 
United  States  Navy  were  put  out  of  commission  in  a  period  of 
less  than  ten  months  by  burnt-out  boiler  tubes.  A  thorough 
inspection  of  the  main  engines  showed  that  only  a  very  ordinary 
amount  of  oil  was  found  in  the  exhaust  steam.  Examination 
of  the  auxiliaries,  however,  disclosed  the  trouble,  which  was 
located  in  the  exhaust  from  six  100-kw.  capacity  lighting  sets, 
which  were  in  operation  day  and  night.  No  lubrication  was 
used  in  the  cylinders,  but  a  careful  test  showed  the  presence  of 
2.2  ounces  of  oil  per  hour  in  the  exhaust  from  each  engine. 
These  engines  were  of  the  forced  lubrication  enclosed  type,  and 
the  oil  was  drawn  up  from  the  crank  chamber  and  crept  along 
the  piston  rods  into  the  cylinders.  When  this  trouble  was 
overcome  by  lengthening  the  distance  pieces  between  the  cyl- 
inders and  the  crank  chamber  top,  and  no  oil  was  found  any 
longer  in  the  exhaust  from  these  engines,  a  great  drop  in  the 
economy  was  at  once  noticed,  the  steam  consumption  increasing 
to  36.3  Ib.  of  steam  per  kw.  hour,  whereas  under  the  old  condi- 
tions the  engines  had  passed  the  United  States  Navy  require- 
ments of  "a  steam  consumption  not  exceeding  31  Ib.  per  kw. 
hour/7  without  lubrication  of  the  cylinders. 

However,  as  has  been  explained,  the  cylinders  were  really 
getting  lubrication,  although  the  oil  was  only  a  light-bodied  oil 
from  the  crank  chambers.  A  series  of  tests  was  then  made  on 
one  of  the  redesigned  engines,  to  determine  the  effect  upon  the 
economy  of  varying  quantities  of  cylinder  oiL  The  trials  showed 
that  when  the  oil  feed  was  cut  very  fine  the  consumption  of 
steam  per  kw.  hour  increased  rapidly.  The  lowest  steam  con- 


376  PRACTICE  OF  LUBRICATION 

sumption  with  ample  internal  lubrication  was  found  to  be 
29.7  Ib.  per  kw.  hour,  compared  with  36.3  Ib.  per  kw.  hour  when 
the  engines  were  operating  without  internal  lubrication.  The 
difference  in  the  steam  consumption  is  partly  due  to  increased 
consumption  of  power  to  overcome  the  internal  friction,  and 
partly  to  the  heavy  leakage  of  steam  past  the  piston  rings  due 
to  the  absence  of  the  oil  film.  Further,  when  the  film  of  oil  is 
not  present  on  the  cylinder  walls  of  steam  engines,  radiation  of 
the  heat  from  the  steam  more  easily  takes  place,  the  oil  film  being 
a  bad  conductor  of  heat. 

These  trials  show  very  clearly  that  the  economy  of  a  recipro- 
cating vertical  engine  is  to  a  very  great  extent  dependent  upon 
proper  lubrication  of  the  cylinders. 

When  this  is  the  case  with  vertical  engines,  it  is  obvious  that 
proper  cylinder  lubrication  is  still  more  important  with  hori- 
zontal steam  engines. 

CYLINDER  OIL  CONSUMPTION 

The  oil  consumption  is  dependent  upon  many  conditions  which 
will  be  briefly  referred  to  in  the  following. 

Large  engines  require  less  cylinder  oil  per  B.H.P.  hour  than  small 
engines. 

Horizontal  engines  obviously  need  more  cylinder  oil  than  vertical 
engines,  but  care  should  be  taken  not  to  underfeed  vertical  en- 
gines, even  if  they  do  not  "  complain, "  as  it  means  extra  friction 
and  loss  of  steam  through  leakage. 

Large  engines  without  tail  rods  require  more  oil  than  when  tail 
rods  are  fitted,  which  relieve  the  pressure  between  the  piston 
and  the  cylinder. 

Steam  Pressure  and  Temperature. — The  greater  the  steam  pres- 
sure, the  higher  the  temperature,  but  when  oils  are  chosen  to  suit 
the,  temperature,  the  oil  consumption  cannot  be  said  to  be  influ- 
enced by  the  steam  pressure  or  the  steam  temperature. 

Superheated  steam  c}oes  not,  as  many  appear  to  think,  mean  an 
increased  oil  consumption;  speaking  generally,  it  may  be  said 
that  the  consumption  for  engines  employing  superheated  steam, 
other  things  being  equal,  need  not  be  more,  in  fact  may  be  slightly 
less  than  with  dry  saturated  steam.  Where  the  steam  is  dirty, 
the  oil  must  be  applied  in  the  best  possible  manner  and  as  econo- 
mically as  possible. 

Saturated  Steam. — Wet,  saturated,  steam  means  an  increased 
demand  for  cylinder  oil,  quite  independent  of  whatever  kind  of 
impurities  may  enter  with  the  wet  steam. 


STEAM  ENGINES  377 

The  oil  consumption  figures  in  Table  No.  17,  given  in  grains  per 
B.H.P.  hour,  may  be  considered  approximately  correct  for  aver- 
age conditions.  The  higher  figures  in  each  case  apply  to  smaller 
engines  or  wet  steam  conditions,  while  the  lower  figures  apply  to 
larger  engines  or  engines  employing  dry  or  superheated  steam, 
or  vertical  engines,  marine  engines  in  particular. 

TABLE  17. — CYLINDER  OIL  CONSUMPTIONS  IN  GRAMS  PER  B.H.P.  HOUR 

Horsepower  Horizontal  engines  Vertical  engines 

Steam  engines  below  400 1 . 0-0 .3  0 . 6-0 . 15 

Steam  engines  above  400 0.6-0.15  0 . 4-0 . 05 

SELECTION  OF  OIL 

The  object  df  internal  lubrication  in  a  steam  engine  is,  firstly,  to 
form  a  lubricating  film  between  the  rubbing  surfaces  and  thus 
replace  the  metallic  friction  with  fluid  friction  as  far  as  possible; 
secondly,  to  form  an  oil  sealing  film  in  order  to  prevent  leakage 
of  steam  past  the  valves,  pistons  and  gland  packings. 

Only  by  feeding  the  correct  grade  of  high  quality  cylinder  oil, 
specially  selected  to  suit  the  operating  conditions  of  the  engine, 
applied  in  the  correct  manner,  to  the  right  place  and  in  the  right 
quantity,  will  the  steam  engine  continue  to  operate  at  its  highest 
efficiency  and  with  a  minimum  cost  of  renewals  and  repairs. 

Perfect  lubrication  is  therefore  chiefly  dependent  on  the  me- 
thods of  lubrication  employed  and  the  selection  of  the  correct  oil 
for  each  individual  case. 

If  too  much  oil  be  used,  lubrication  under  saturated  steam  con- 
ditions will  not  be  any  better  than  when  the  right  quantity  of 
oil  is  used';  whereas  under  superheated  steam  conditions,  the 
excess  oil  is  detrimental,  leading  to  the  formation  of  carbonaceous 
deposits. 

If  too  little  oil  be  used,  a  satisfactory  oil  film  will  not  be  main- 
tained between  the  frictional  surfaces,  so  that  not  only  will 
heavy  friction  and  wear  occur,  but  also  excessive  steam  leakage. 

There  are  a  few  vertical  engines  employing  saturated  steam 
which  can  be  operated  without  the  use  of  cylinder  oil  and  without 
groaning.  Non-lubrication  will,  however,  mean  excessive  friction 
and  excessive  leakage  of  steam  past  the  moving  surfaces,  which 
will  be  worth  many  times  the  cost  of  good  lubrication. 

If  an  oil  too  heavy  in  viscosity  is  used  it  will  not  atomize  readily, 
resulting  in  poor  distribution,  and  necessitating  excessive  con- 
sumption. Due  to  its  heavy  body,  the  fluid  frictional  losses  will 
be  higher  than  they  need  be,  and  if  the  steam  carries  over  impuri- 
ties to  the  engine,  the  use  of  such  an  oil  will  encourage  the  accumu- 


378  PRACTICE  OF  LUBRICATION 

lation  of  deposits,  particularly  under  conditions  of  high  pressure 
and  superheat. 

If  an  oil  too  light  in  viscosity  be  used,  it  will  readily  atomize  and 
distribute  itself,  but  it  will  not  be  able  to  withstand  the  pressure 
between  the  rubbing  .surfaces;  metallic  contact  will  take  place, 
resulting  in  excessive  wear;  also,  excessive  leakage  of  steam  will 
occur,  owing  to  the  rubbing  surfaces  not  being  completely  oil 
sealed. 

With  the  right  quality  oil  in  use,  correctly  selected  for  the  con- 
ditions and  applied  in  right  quantity,  a  satisfactory  lubricating 
film  will  be  maintained  on  all  the  internal  surfaces.  This  film 
will  be  maintained  with  a  lower  consumption  of  oil  than  with 
any  other  grade  of  oil.  Therefore  the  cost  of  lubrication  will  be 
low  and  the  frictional  losses,  due  to  the  fluid  friction  of  the  oil 
itself  as  well  as  the  leakage  of  steam  past  the  moving  surfaces, 
will  be  reduced  to  a  minimum. 

For  conditions  of  high  pressure  and  superheat,  the  use  of  the 
right  quality  cylinder  oil  will  also  mean  that,  rightly  applied  and 
in  the  right  quantity,  the  danger  of  the  formation  of  carbonaceous 
deposits  will  be  minimized,  and  the  possibility  of  excessive  wear 
much  reduced. 

In  the  following  pages  will  be  examined  the  conditions  influ- 
encing the  selection  of  the  correct  grade  of  cylinder  oil,  namely, 
steam  pressure,  size  and  construction,  superheat,  wet  steam, 
load,  impurities,  exhaust  steam. 

Influence  of  Steam  Pressure. — High  steam  pressure  means  high 
temperature,  so  that  speaking  generally,  heavy  viscosity  oils  are 
used  for  high  steam  pressures  and  low  viscosity  oils  for  low  steam 
pressures  (low  pressure  cylinders  in  particular) . 

Influence  of  Size,  Speed,  and  Construction. — The  weight  of  a 
piston  increases  very  nearly  as  the  cube  of  its  diameter,  but  its 
bearing  surface  more  as  the  square,  so  that  large  pistons  in  hori- 
zontal engines,  when  they  are  not  supported  by  a  tail  rod,  require 
very  heavy  viscosity  oils.  Smaller  pistons  and  all  vertical  cyl- 
inders, other  things  being  equal,  will  be  best  served  with  lower 
viscosity  oils.  High  piston  speed,  which  is  found  in  most  modern 
engines,  particularly  superheated  steam  engines,  demands  lower 
viscosity  oils,  so  as  to  minimize  the  oil  drag  on  the  pistons. 

Influence  of  Superheated  Steam. — When  steam  of  moderate 
superheat  is  used,  it  will  enter  the  high  pressure  cylinder  in  a  dry 
condition,  but  during  the  expansion  of  the  steam  in  the  cylinder 
it  will  cool,  and  toward  the  end  of  the  stroke  condensation  will 
occur. 

In  the  case  of  highly  superheated  steam,  it  is  of  the  greatest 


STEAM  ENGINES  379 

.importance  that  the  oil  should  be  thoroughly  atomized  in  the 
body  of  the  steam.  There  is  no  condensation,  therefore  no 
washing  effect  on  the  cylinder  walls.  The  oil  remains  a  long 
time  in  the  high  pressure  cylinder,  exposed  to  friction  and  heat; 
while  ,therefore,  only  a  small  quantity  of  oil  is  required,  it  should 
be  of  such  a  nature  that  it  will  withstand  the  heat  without  appre- 
ciable decomposition  and  resultant  formation  of  carbon. 

Dark  cylinder  oils  exposed  to  heat  will  form  more  carbon  than 
filtered  cylinder  oils.  The  coloring  matter,  which  is  extracted 
during  the  filtration  process  consists  of  very  high  specific  gravity 
bituminous  matter  (hence  the  reason  why  filtered  cylinder  oils 
have  low  specific  gravities),  which  evidently  decomposes  and 
forms  carbon. 

It  has  been  asserted  by  oil  firms  that  dark  cylinder  oils  are 
better  lubricants  than  filtered  cylinder  oils.  They  are  as  a  rule 
more  viscous,  which  may  perhaps  excuse  this  fallacy  of  opinion, 
but  a  moment's  reflection  will  make  it  obvious  to  anyone  that 
the  chief  difference  between  filtered  and  dark  cylinder  oils  is  that 
the  latter  contain  bituminous  coloring  matter,  the  greater 
portion  of  which  is  removed  when  manufacturing  filtered  cylinder 
oils;  in  other  words,  that  the  higher  viscosity  of  dark  cylinder 
oils  is  largely  due  to  sticky  non-lubricating  ingredients,  which 
are  liable  to  decomposition  exposed  to  heat  and  other  influences.- 

As  regards  compounding  superheat  cylinder  oils,  the  author 
recommends  a  small  percentage,  say,  4  per  cent,  to  6  per  cent, 
acidless  tallow  oil,  for  most  conditions  of  superheat,  as  the 
fixed  oil  improves  lubrication  appreciably. 

The  oil  becomes  very  thin  due  to  the  high  temperature,  and 
the  fixed  oil  improves  the  oiliness  of  a  straight  mineral  oil;  its 
presence  is  therefore  nearly  always  desirable.  No  ill  effects 
have  ever  been  known  to  be  caused  by  decomposition  (formation 
of  fatty  acid)  of  such  a  small  percentage  of  fixed  oil.  On  the 
contrary,  it  will  tend  to  prevent  carbonized  matter  baking 
together  and  forming  hard  crusts,  in  this  way  making  the  nature 
of  such  deposits  less  dangerous. 

Influence  of  Wet  Steam. — Where  the  steam  is  wet  it  has  a 
tendency  to  wash  away  the  oil  film  on  the  internal  surfaces.  In 
compound  or  triple  expansion  engines,  even  if  the  steam  is  dry 
on  entering  the  high  pressure  cylinder,  the  fall  in  pressure  and 
expansion  taking  place  produces  condensation,  so  that  the  steam 
arriving  at  the  low  pressure  cylinder  usually  is  very  wet. 

It  is  obvious  that  the  problem  of  lubricating  the  high  pressure 
cylinder  under  dry  steam  conditions  is  different  from  lubricating 
the  high,  pressure  cylinder  under  wot  steam  conditions,  or  from 


380  PRACTICE  OF  LUBRICATION 

lubricating  the  low  .pressure  cylinders  under  very  wet  steam 
conditions. 

In  order  to  lubricate  cylinders  satisfactorily  under  wet  steam 
conditions,  the  cylinder  oil  must  readily  combine  with  the  mois- 
ture and  cling  to  the  cylinder  walls,  i.e.,  it  must  be  a  compounded 
cylinder  oil.  It  is  therefore  frequently  desirable  to  use  one 
grade  of  cylinder  oil  for  the  high  pressure  cylinder,  and  a  different 
grade  of  cylinder  oil  (lower  viscosity,  more  heavily  compounded) 
for  the  low  pressure  cylinder  in  large  compound  or  triple  expansion 
engines. 

Influence  of  Engine  Load. — The  greater  the  engine  load  the 
greater  is  the  volume  of  steam  passing  through  the  steam  pipe 
into  the  engine;  and  the  higher  its  velocity,  the  better  will  it  be 
able  to  break  up  the  cylinder  oil  introduced  through  the  atomizer. 

As  superheated  steam  does  not  atomize  and  distribute  the  oil 
so  well  as  does  saturated  steam,  engines  employing  superheated 
steam  and  likely  to  operate  under  light  load  conditions  should 
have  means  for  lubricating  the  internal  parts  direct  in  addition 
to  introducing  the  oil  where  it  can  be  atomized.  Light  load  also 
means  that  the  steam  expands  more  in  the  high  pressure  cylinder, 
so  that  at  the  end  of  the  piston  stroke,  the  steam  is  much  more 
moist  (more  condensation)  than  under  full  load  conditions. 
Wet  steam,  calls  for  compounded  cylinder  oil,  so  that  speaking 
generally,  light  load  conditions  demand  compounded  oils  of  low 
viscosity. 

Influence  of  Impurities  in  the  Steam. — It  has  already  been 
mentioned  how  iron  oxides,  boiler  salts,  etc.,  have  the  effect  of 
combining  with  the  oil  and  forming  deposits.  The  higher  the 
viscosity  of  the  oil  the  more  difficult  will  it  be  to  avoid  such 
deposits,  as  such  oils  cling  tenaciously  to  the  impurities.  Low 
viscosity  oils  are  therefore  to  be  preferred,  where  a  great  deal  of 
impurities  enter  with  the  steam;  this  is  particularly  the  case 
under  conditions  of  superheat. 

As  the  presence  of  impurities  in  the  steam  usually  means  that 
priming  of  the  boilers  is  responsible,  in  the  first  instance,  the 
steam  will  also  be  wet,  so  that  oils  heavily  compounded  are  as  a 
rule  called  for.  There  is  one  exception  to  this  rule,  this  namely, 
that  under  conditions  of  high  superheat,  where  it  is  only  the 
dry  boiler  salts  that  reach  the  engine,  and  where  these  dry  salts 
contain  alkali  (soda,  for  example),  they  will  form  a  soap  with  the 
tallow  oil  present  in  the  cylinder  oil,  which  will  aggravate  the 
deposit  trouble,  whereas  with  a  straight  mineral  oil  such  soap 
cannot  possibly  be  formed. 

For  saturated  low  pressure  steam  conditions,  there  is  no  c/ 


STEAM  ENGINES  381 

difference  between  dark  or  filtered  cylinder  oils  as  regards  forma- 
tion of  deposit  by  impurities;  but  for  superheated  steam  condi- 
tions filtered  cylinder  oils  are  vastly  superior,  as  under  the  dry 
high  temperature  conditions  the  bituminous  matter  in  dark  oils 
combines  with  the  impurities,  decomposes,  due  partly  to  oxidation 
(oxygen  being  taken  from  the  iron  oxides,  for  example)  and  forms 
hard  brittle  carbon. 

Speaking  generally,  the  presence  of  impurities  under  saturated 
steam  conditions  therefore  calls  for  oils  of  low  viscosity  and  com- 
pounded (filtered  oils  not  particularly  needed);  whereas  impuri- 
ties under  superheated  steam  conditions  demand  mineral  oils 
of  low  viscosity  and  filtered  (compounded  oils  may  form  soap) . 

Influence  of  Exhaust  Steam. — As  mentioned  elsewhere  it  is 
under  certain  conditions  desirable  to  extract  the  oil  from  the 
exhaust  steam  and  to  eliminate  as  far  as  possible  the  danger 
arising  from  oil  getting  back  into  the  boiler.  All  compounded 
cylinder  oils  are  difficult  to  separate  from  the  exhaust  steam  and 
from  the  feed  water.  All  straight  mineral  oils  are  fairly  easy 
to  extract,  but  the  dark  oils  combine  rather  intimately  with  the 
water,  forming  semi-emulsified  clots  of  oil  (which  cannot  be  used 
again)  and  just  a  trace  of  the  oil  goes  into  a  fine  emulsion. 

Well  filtered  straight  mineral  oils  separate  easily  from  the 
feed  water  and  the  oil  can  be  recovered  and  used  on  less  important 
work;  the  feed  water  will  be  practically  free  from  emulsified  oil. 

It  will,  however,  be  found  that  more  oil  is  required  when 
using  a  straight  mineral  cylinder  oil  than  when  using  a  com- 
pounded cylinder  oil,  so  that  the  best  results  will  often  be  pro- 
duced by  using  a  slightly  compounded  filtered  oil,  as  such  an  oil 
will  give  more  efficient  and  more  economical  lubrication.  The 
oil  should  be  fed  as  economically  as  possible,  so  that  there  will 
be  only  a  small  quantity  of  oil  present  in  the  exhaust  steam. 
Diagrams  Nos.  1  to  6  may  prove  of  interest  in  connection  with 
the  influence  of  exhaust  steam  on  the  selection  of  oil. 


382 


PRACTICE  OF  LUBRICATION 


DlAGKAM    No.    1 

SMALL,  NON-CONDENSING  LAND  ENGINICS 

,60/Letr 

^x^\ 

STCAM  TRAP 


ALTERNATIVELY .' 
EXHAUST  STEAM  MAY  Bf 


CONTACT  ft fD 
VMTttt  H£AT£R 


FEED  PUMP 


When  the  exhaust  steam  is  discharged  into  the  atmosphere,  the  cylinder 
oil  may  be  chosen  entirely  with  a  view  to  suit  the  engine  requirements. 

When  a  contact  feed  water  heater  is  fitted,  straight  mineral,  dark  or 
filtered  steam  cylinder  oils  must  be  vised. 


DIAGRAM  No.  2. 
LARGER  SIZE  NON-CONDENSING  LAND  ENGINES 

.BOILERS 


FEED  PUMP 


STEAM  TRAP 


EXHAUST  STEAM 
OIL  SEPERATOR 


STEAM  FOR  HEATIH6 
OR  PRYING  PURPOSES 


Straight  mineral,  dark  or  filtered  cylinder  oils  must  be  used,  or  filtered 
oils,  slightly  compounded,  used  very  sparingly. 

With  some  vertical  engines,  aquadag  has  been  used  successfully,  and  the 
condensed  steam  from  the  heating  system  returned  to  the  boilers.  (See 
page  151). 


STEAM  ENGINES 


383 


DIAGRAM  No.  3 
SURFACE-CONDENSING  ENGINE  IN  ICE-MAKING  PLANTS 

FE  EP  PUMP 


EXHAUS7<7EAM 
OIL  SEPERA70R 


H07-WELL 


WA7ER  RE-BOILER 


/SAHD  FIL7ER 

Straight  mineral,  dark  or  filtered  oils  must  be  used,  or  filtered  oils,  slightly 
compounded,  used  very  sparingly. 


DIAGRAM  No.  4 
MARINE  ENGINES 


BOILERS 


.S7EAM  TRAP 


EXHAUS7  STEAM 
OIL  SEPERATOR 
'Rarely  Fitted) 


H07  WELL 


I  FEED  PUMP 
I  FE EP  WA 7ER  HEA7E.R 


Straight  mineral,  dark  or  filtered  oils  must  be  used,  but  when  an  exhaust 
steam  oil  separator  is  fitted,  filtered  oils  lightly  compounded  are  recom- 
mended and  will  give  efficient  lubrication;  they  can  and  must  be  used  very 
sparingly. 


384 


PRACTICE  OF  LUBRICATION 


DIAGRAM  No.  5 
LARGE  SURFACE  CONDENSING  ENGINES  IN  LAND  POWER  PLANTS 


\50ILERS 


STEAM  TRAP 


STEAM  EH&IHE 


EXHAUST  STEAM 
OILSEPERATOR 


I  DE-OIL1HO  PLAHT 
"FEED  PUMP 

The  oil  may  be  chosen  entirely  with  a  view  to  suit  the  engine  requirements, 
as  every  trace  of  oil  is  eliminated  from  the  feed  water  in  the  deoiling  plant. 

DIAGRAM  No.  6 
LARGE  OR  SMALL  JET  CONDENSING  ENGINES 

\BOILERS 


\STEAM  TRAP 


TEAM  EH6IHE 


EXHAUST5TE/IM 
OILSEPERATOR 


^    SCOURIHG  PURPOSES  IN  WOOL  L  EM 
OR  WORSTED  MILLS,  LAUHDRIES,  ETC. 


HOT  WATER  RUH  TO  MS  TE,  O£  COOL  ED 
A  HP  USED  AGJIH,  Off  USED  FOR 


HOT  WELL 


FEED  PUMP 


When  an  exhaust  steam  oil  separator  is  fitted,  the  oil  may  be  chosen 
entirely  with  a  view  to  suit  the  engine  requirements;  when  no  oil  separator 
is  fitted,  and  when  the  hot  condenser  water  is  used  and  comes  in  contact 
with  textile  fabrics,  heavily  compQundec|  ojls  must  not  be  used. 


STEAM  ENGINES  385 

TESTING  CYLINDER  OIL 

The  oil  should  be  tested  for  a  period  of  at  least  three  months  in 
case  the  first  few  days'  working  has  been  satisfactory.  It  takes 
time  for  a  good  cylinder  oil  to  produce  a  good  working  skin  on 
the  internal  wearing  surfaces ;  in  fact,  it  takes  much  longer  than 
for  an  unsuitable  cylinder  oil  to  destroy  the  good  surface  produced 
by  a  suitable  oil.  After  a  few  days  the  consumption  of  oil  should 
be  gradually  decreased  and  the  minimum  feed  determined  by 
which  smooth  and  satisfactory  running  can  be  accomplished.  At 
the  end  of  three  months'  working  on  the  reduced  feed  the  cylin- 
ders should  be  opened  up  for  inspection  and  should  present  a  sur- 
face of  rather  dull  appearance,  coated  with  a  film  of  oil. 

The  same  remarks  will  apply  to  the  appearance  of  valve  rods, 
piston  rods,  valves  and  valve  faces.  Whenever  a  change  of  cyl- 
inder oil  is  made,  irregularities  may  be  experienced  during  the 
earlier  period  of  its  working,  due  to  the  new  oil  altering  the  wearing 
surfaces.  Where  unsuitable  oils  have  been  in  use,  and  various 
deposits  have  accumulated  behind  the  piston  rings  and  in  the 
glands,  cylinder  oil  of  a  good  grade  will  clean  the  surfaces.  In  such 
cases  dirt  may  be  carried  out  on  to  the  piston  rod  and  the  new  oil 
generally  gets  the  blame. 

PHYSICAL  AND  CHEMICAL  TESTS 

Before  giving  specific  recommendations  for  different  types  of 
steam  engines  it  may  be  well  to  examine  briefly  the  physical  and 
chemical  tests  most  often  referred  to  when  judging  the  merits  of 
cylinder  oils. 

These  are:  specific  gravity,  viscosity,  flash  point,  percentage 
and  nature  of  compound,  color,  cold  test,  and  loss  by  evaporation. 

Specific  Gravity. — The  lower  the  specific  gravity  for  oils  of 
similar  viscosity,  the  purer  is  the  oil.  A  highly  filtered  cylinder 
oil  will  be  lower  in  specific  gravity  than  one  less  purified.  It  must 
be  kept  in  mind  that  these  statements  are  true  only  because  prac- 
tically all  steam  cylinder  oils  are  produced  from  paraffin  base 
crudes,  which  are  rather  similar  in  nature. 

Viscosity. — The  viscosity  taken  at  212°F.  is  always  useful.  It 
has  been  often  referred  to  in  the  preceding  pages  regarding 
"Influencing  Conditions." 

The  admixture  of  tallow  oil  reduces  the  viscosity  but  increases 
the  lubricating  power  of  the  oil — its  oiliness .  Filtered  cylinder  oils 
have  lower  viscosity  than  dark  cylinder  oils,  but  greater  friction 
reducing  powers.  In  comparing  viscosities  of  different  oils,  one 

25 


,  386  PRACTICE  OF  LUBRICATION 

must  therefore  keep  in  mind  whether  they  are  compounded  or 
more  or  less  filtered. 

Flash  Point. — Although  it  is  true  that  good  cylinder  oils  for 
use  with  superheated  steam  do  possess  a  fairly  high  flash  point, 
yet  it  is  by  no  means  certain  that  a  cylinder  oil  having  a  high 
flash  point  is  suitable  for  work  with  superheated  steam.  The 
flash  point  is  determined  in  the  laboratory  under  atmospheric 
conditions.  If  the  cylinder  oil  were  to  be  tested  under  the  high 
pressure  carried  in  the  steam  pipe  the  flash  point  would  un- 
doubtedly be  shown  to  be  considerably  higher,  just  as  the  boiling 
point  of  water,  which  at  atmospheric  pressure  is  212°F.,  increases 
with  any  pressure  above  that  of  the  atmosphere  (for  instance  at 
150  Ib.  per  square  inch  the  boiling  point  of  water  is  366°F.). 
This  will  explain  why  it  is  frequently  possible  to  use  a  cylinder  oil 
successfully  for  lubrication  under  superheated  steam  conditions 
where  the  temperature  of  the  steam  is  even  a  good  deal  higher  than 
the  flash  point  oj  the  oil,  measured  under  atmospheric  conditions. 

Besides,  there  is  practically  no  air  present  in  the  steam,  and 
therefore  no  danger  of  the  oil  flashing  anywhere.  The  tempera- 
ture of  the  piston  or  valve  rods,  which  are  the  only  hot  frictional 
parts  passing  out  into  'the  atmosphere,  is  always  considerably 
lower  than  the  maximum  steam  temperature,  so  that  the  flash  point 
of  the  oil  is  never  reached;  and  even  if  it  were  reached,  nothing 
jmuch  would  happen,  there  being  no  chance  of  an  explosive 
mixture  being  formed  of  oil  vapor  and  air,  such  as  may  be  the 
case  in  air  compressors. 

Compounded  Oils. — For  most  conditions,  experience  has  proved 
that  cylinder  oils  compounded  with  the  proper  kind  and  amount 
of  fixed  oil  are  more  suitable  than  cylinder  oils  which  are  straight 
mineral.  It  is  more  particularly  where  steam  engines  are  work- 
ing with  wet  steam  that  the  advantage  of  using  compounded  oils 
becomes  apparent.  Great  care  must  be  exercised  in  selecting  the 
proper  kind  of  fixed  oil,  as  unsuitable  fixed  oils  under  the  action  of 
steam  at  high  pressure  and  temperature  decompose  and  develop 
acids  and  gummy  residues  which  corrode  the  internal  wearing- 
surfaces  and  produce  sticky,  pasty  deposits  which  unduly  increase 
friction.  Compounding  mineral  cylinder  oils  with  the  right 
proportion  (from  4  per  cent,  to  15  per  cent.)  and  quality  of  fixed  oil, 
preferably  acidless  tallow  oil,  usually  adds  to  its  lubricating 
value  and  better  results  will  be  secured  than  if  the  cylinder  oil 
was  used  without  the  admixture  of  fixed  oil. 

Color. — The  more  highly  filtered  a  cylinder  oil  is  the  lighter  will 
it  be  in  color,  so  that  light  color  (low  Lovibond  color  number) 
usually  signifies  a  high  degree  of  purity. 


STEAM   ENGINES  387 

Cold  Test.  — It  is  desirable  that  a  cylinder  oil  keeps  fairly  fluid 
at  ordinary  engine  room  temperatures,  especially  when  used 
through  hydrostatic  lubricators,  with  which  difficulty  is  always 
experienced  in  feeding  viscous  cylinder  oils  at  a  regular  rate  of 
feed.  When  good  mechanically  operated  lubricators  are  employed, 
the  cold  test  of  the  cylinder  oil  is  of  less  importance. 

Loss  by  Evaporation. — Such  laboratory  tests  as  determine  the 
percentage  of  evaporation  when  heating  a  sample  of  cylinder  oil 
to  a  certain  temperature  for  a  certain  time  are  of  very  little  value 
in  determining  lasting  properties  of  a  cylinder  oil,  as  these  tests 
are  carried  out  under  atmospheric  pressure  and  under  conditions 
greatly  different  from  those  met  with  in  actual  work. 

It  will  be  understood  from  the  above  that  the  author  considers 
the  following  tests  of  great  importance. 

Specific  gravity  and  color — as  indicating  degree  of  purity. 

Viscosity — to  suit  conditions  of  temperature  and  pressure. 

Percentage  and  nature  of  compound — to  suit  wet  steam  condition 
and  increase  oiliness. 

Cold  test  (equivalent  to  viscosity  at  low  temperatures)— to 
ensure  proper  feeding  of  the  oil  through  the  lubricators. 

THE   USE   OF   TALLOW   MIXTURES   AND    SEMI-SOLID    GREASES 
AS  CYLINDER  LUBRICANTS 

Acidless  tallow  oil  and  not  tallow  is  generally  used  for  com- 
pounding cylinder  oils,  because  tallow  is  often  acid  or  rancid  and 
therefore  inferior  to  acidless  tallow  oil.  Tallow  and  black  lead 
used  to  be  a  favorite  cylinder  lubricant  at  sea,  when  steam  pres- 
sures were  low;  but  with  the  advent  of  higher  steam  pressures 
such  mixtures  have  almost  disappeared.  Yet  it  is  not  infrequent 
to  find  engine  drivers  both  of  stationary  and  locomotive  engines 
in  the  habit  of  using  tallow  indiscriminately,  particularly  under 
wet  steam  conditions;  it  keeps  the  engine  quiet  and  makes  the 
cylinder  oil  last  longer.  The  acidity  produced  by  decomposition 
of  the  tallow  (into  fatty  acid  and  glycerine)  will  however  in  time 
act  most  destructively  on  all  cast-iron  surfaces.  A  symptom 
often  exhibited  is  that  the  acid  "perforates"  the  skin  on  the 
piston  rods,  the  rod  becomes  pitted  and  wears  badly.  It  also 
causes  deposits  inside  the  valve  chests  and  cylinders,  composed 
chiefly  of  iron  soaps  and  may  soon  cause  sufficient  corrosion  and 
pitting  to  ruin  the  surfaces  after  a  comparatively  short  life. 

In  locomotives  a  portion  of  the  deposits  reaches  the  smoke  box 
exhaust  nozzle  and  cakes,  due  to  the  great  heat,  closing  tho  nozzle 
and  causing  a  labored  exhaust  until  cleared  away. 


388  PRACTICE  OF  LUBRICATION 

Cast-iron,  long  exposed  to  the  action  of  fatty  acids  from  tallow 
becomes  so  crumbly  that  it  can  be  cut  with  a  knife  like  cheese. 
The  metal  is  porous  and  filled  with  iron  soaps,  etc.,  which  explains 
why  it  is  so  exceedingly  difficult  to  introduce  an  oil,  largely  min- 
eral in  character,  where  tallow  (or  for  that  matter  any  fixed  oil, 
such  as  rape  oil — Colza — occasionally  favored  by  engine  drivers 
for  troublesome  engines),  or  cylinder  oils  containing  a  large 
percentage,  say  20  per  cent.-25  per  cent,  or  more  of  tallow, 
tallow  oil,  or  other  fixed  oil,  has  been  in  use  for  a  long  period. 

The  only  way  is  to  introduce  the  oil  very  gradually  mixed  with 
the  old  lubricant  over  a  period  of  at  least  3  months,  gradually 
increasing  the  percentage  so  as  to  give  the  acid  products  of 
decomposition  time  to  loosen,  dissolve  and  get  cleared  away 
through  the  exhaust.  If  the  oil  is  introduced  too  quickly, 
it  will  dissolve  the  deposits  too  rapidly,  with  the  result  that 
excessive  scoring  and  wear  inevitably  take  place,  and  a  return  to 
the  old  lubricant  becomes  necessary  if  the  engine  is  not  to  suffer 
more  serious  damage. 

In  America  semi-solid  greases,  containing  more  or  less  tallow, 
are  not  infrequently  used  as  cylinder  lubricants.  They  are  more 
difficult  to  apply  economically  than  a  proper  grade  of  cylinder 
oil,  and  cannot  possibly  give  better  lubrication,  as  they  either 
contain  a  percentage  of  non-lubricating  material,  or,  if  they  are 
rich  in  tallow  and  such  like,  give  rise  to  troubles  with  corrosion 
of  surfaces  or  with  the  feed  water  (too  much  compound) .  Weight 
for  weight  cylinder  oil  of  the  correct  grade  is  always  preferable, 
and  besides  it  will  be  found  that  if  the  price  per  pound  is  com- 
pared with  that  of  semi-solid  grease,  the  latter  is  always  dearer. 
The  use  of  such  lubricants  cannot  therefore  be  recommended  from 
any  point  of  view,  except  perhaps  that  of  the  manufacturer. 

LUBRICATION  CHART 

The  lubrication  chart  No.  10,  shown  on  page  390,  gives  specific- 
cylinder  oil  recommendations  for  all  types  of  steam  engines. 
Before  describing  how  the  chart  is  to  be  used,  it  will  be  necessary 
to  describe  what  the  various  grades  of  cylinder  oil  represent. 

Cylinder  oils  of  four  viscosity  ranges,  Nos.  1,  2,  3  and  4,  have 
been  found  adequate  for  the  lubrication  requirements  of  all 
types  and  sizes  of  steam  engines.  These  viscosity  ranges  are 
shown  in  Table  No.  18,  also  the  approximate  specific  gravities, 
flashpoints  and  cold  tests,  corresponding  to  these  viscosities,  for 
both  filtered  and  dark  oils. 

There  is  no  demand  for  dark  oils  of  No.  1  viscosity,  and  it  is  not 


STEAM  ENGINES 


389 


possible  commercially  to  manufacture  filtered  oils  of  No.  4 
viscosity,  nor  do  the  actual  requirements  call  for  such  oils. 
Filtered  oils  of  No.  3  viscosity  are  superior  to  dark  oils  of  No.  4 
viscosity  as  regards  oiliness  (which  is  more  important  than  vis- 
cosity), but  they  are  more  expensive  to  manufacture.  The 
various  oils  may  also  be  straight  mineral  or  more  or  less  heavily 
compounded  with  acidless  tallow  oil. 

There  are  a  few  dark  cylinder  oils  marketed  having  higher 
viscosities  and  flashpoints  than  No.  4  viscosity  range.  Such  oils 
are  unnecessarily  viscous,  waste  power,  and  easily  carbonize 
and  form  deposits. 

In  Table  No.  19  are  indicated  twelve  grades  of  cylinder  oils, 
six  filtered  oils  and  six  dark  oils,  representing  the  author's  recom- 
mendations based  on  practical  experience  with  such  oils  on  a 
vast  number  of  steam  engines. 

TABLE  No.   18. — VISCOSITY  RANGE,  ETC.,  OF  CYLINDER  OILS 


Cylinder  oil 

Saybolt 
viscosity 
at212°F., 
sec. 

Specific 
gravity 

Open  flash-    Cold  test, 
point,  °F.            °F. 

Filtered 

M 

k 

& 

Filtered 

44 

| 

Filtered 

^ 

Jj 

No  1  filtered         

85-105 
115-135 
145-165 
180-200 

0.885 
0.887 
0.890 

0.900 
0.905 
0.910 

500 
525 
550 

520 
530 
580 

40-50 
50-60 
50-60 

40-50 
40-50 
50-60 

No  2  dark  No  2  filtered         

No.  3  dark,  No.  3  filtered  '  
No  4  dark                                  

TABLE  No.  19. — 12  GRADES  OF  CYLINDER  OILS 

Designation 

No.  1  filtered  cylinder  oil,  heavily  compounded  (10  per  cent.) .  No.  1  F.H.C. 

No.  1  filtered  cylinder  oil,  lightly  compounded  (4  per  cent.) No.  1  F.L.C. 

No.  2  filtered  cylinder  oil,  medium  compounded  (6  per  cent.) No.  2  F.M.C. 

No.  3  filtered  cylinder  oil,  medium  compounded  (6  per  cent.) No.  3  F.M.C. 

No.  2  dark  cylinder  oil,  medium  compounded  (6  per  cent.) No.  2  D.M.C. 

No.  3  dark  cylinder  oil,  medium  compounded  (6  per  cent.) No.  3  D.M.C. 

No.  3  dark  cylinder  oil,  heavily  compounded  (10  per  cent.) No.  3  D.H.C. 

.    No.  4  dark  cylinder  oil,  medium  compounded  (6  per  cent.) No.  4  D.M.C. 

No.  2  filtered  cylinder  oil,  straight  mineral No.  2  F.S.M. 

No.  2  dark  cylinder  oil,  straight  mineral No.  2  D.S.M. 

No.  3  filtered  cylinder  oil,  straight  mineral No.  3  F.S.M . 

No.  3  dark  cylinder  oil,  straight  mineral No.  3  D.S.M. 

The  twelve  grades  in  Table  No.  19  will  be  found  in  the  first 
column  of  the  Lubrication  Chart  No.  10,  page  390.  The  other 
vertical  columns  refer  to  the  conditions  influencing  the  choice  of 
cylinder  oil.  The  black  squares  in  each  column  indicate  condi- 
tion for  which  the  cylinder  oil  (shown  at  the  left  extreme  of  the 
same  horizontal  line)  is  not  suitable. 

In  order  to  find  an  oil  suitable  for  a  certain  set  of  conditions, 
take  a  piece  of  paper  and  place  it  with  its  upper  edge  along  the  top 


300 


PRACTICE  OF  LUBRICATION 


LUBRICATION  CHART  NO.  10 
FOR  STEAM  CYLINDERS  AND  VALVES 


Also  Kecommended  for  Large  Low  Pressure  Cylinders  with  Wet  Steam 


NOTE  1. — For  light  load  conditions  choose  an  oil  slightly  lower  in  viscosity 
and/or  more  heavily  compounded  than  the  one  indicated  by  the  chart. 

NOTE  2. — With  impure  steam  (boiler's  priming  etc.)  a  filtered  oil  should 
preferably  be  used,  and  with  saturated  steam  preferably  compounded. 

NOTE  3.— When  the  chart  recommends  more  than  one  grade  the  one  lowest 
in  viscosity  should  preferably  be  chosen  when  a  dark  oil  as  well  as  a  filtered  oil 
is  recommended,  as  will  often  be  the  case;  the  former  unless  there  are  special 
conditions  (NOTE  2)  may  be  preferred  as  it  is  (or  ought  to  be)  lower  in  price. 

NOTE  4. — 'A  straight  mineral  oil  can  always  be  used  in  place  of  the  compounded 
oil  recommended  by  the  chart  but  it  means  an  increased  oil  consumption  as 
compared  with  a  medium  compounded  oil  of  50  per  cent  to  100  per  cent  the 
use  of  a  straight  mineral  oil  in  place  of  a  slightly  compounded  oil  or  the  latter 
in  place  of  a  heavily  compounded  oil  means  an  increase  in  oil  consumption  of 
30  per  cent,  to  50  per  cent. 

NOTE  5. — From  10  per  cent — 15  per  cent  of  compound  may  be  required  in 
case  of  (a)  very  wet  steam  in  large  engines,  low  pressure  cylinders  in  particular; 
(6)  heavily  loaded  Corliss  valves  or  unbalanced  slide  valves;  (c)  very  dirty  steam, 
particularly  saturated  steam. 

NOTE  6. — No.  2  FSM  and  3FSM  will  separate  easier  from  the  exhaust  steam 
and  feed  water  than  No.  2  DSM  and  3  DSM  and  will  give  cleaner  and  better 
lubrication,  particularly  Bunder  conditions  of  super-heated  steam  and/or  impure 
steam. 


STEAM  ENGINES  :W  1 

line,  make  a  pencil  mark  on  (lie  edge  of  Uie  paper  corresponding 
to  each  set  of  conditions  and  opposite  the  condition  found  in  the 
steam  engine  in  question.  It  is  important  that  a  mark  be  made 
corresponding  to  all  seven  groups  of  conditions  in  order  that  the 
recommendation  made  by  the  table  may  be  correct.  Having 
marked  the  paper  at  seven  places,  move  it  down  to  the  first 
horizontal  line;  if  none  of  the  seven  marks  clashes  with  (corre- 
sponds with)  any  of  the  black  squares  on  this  line,  Cylinder  Oil 
No.  1  F.H.C.  (No.  1  filtered,  heavily  compounded  is  the  correct 
grade  of  oil  to  use.  If  one  or  more  of  the  black  squares  clashes 
with  the  pencil  marks,  move  the  paper  down  to  the  next  hori- 
zontal line.  If  there  are  still  obstacles  in  the  way  (black  squares) 
move  to  the  third  line  and  so  on  until  a  line  is  found  where  there 
are  no  obstacles  opposite  the  pencil  marks.  The  correct  oil 
will  then  be  shown  in  column  1  of  that  particular  horizontal  line. 
Do  not  go  from  line  1  to  line  5,  because  the  first  four  lines  all 
refer  to  No.  1  F.H.C.;  they  represent  different  sets  of  conditions 
and  no  lines  must  be  missed. 

LOCOMOTIVES.     CYLINDERS  AND  VALVES 

From  a  lubrication  point  of  view  there  are  two  main  groups  of 
locomotives,  namely,  railway  locos  employed  in  more  or  less 
regular  service  on  railways,  and  works  locos,  such  as  are  employed 
in  steelworks,  mines,  quarries,  shunting  locos,  etc. 

Works  Locomotives. — It  is  often  painful  to  see  the  crude  way  in 
which  lubrication  is  provided  in  most  works  locos.  Many  small 
locos  are  only  fitted  with  tallow  cups,  and  at  best  some  kind  of 
hydrostatic  lubricator — ^as  a  rule  the  cheapest  possible — is 
installed. 

With  tallow  cups,  lubrication  is  always  poor,  whether  the  oil 
allowance  is  great  or  small.  With  hydrostatic  lubricators  there  is 
always  waste  of  oil,  as  they  keep  on  feeding,  quite  independent 
of  the  actual  requirements.  The  drivers  are  not  so  careful  as 
rail  way.  engine  drivers,  and  do  not  as  a  rule  trouble  to  shut  off 
the  lubricator  every  time  the  loco  stops  for  a  little  while.  Me- 
chanically operated  lubricators,  operated  from  one  of  the  valve 
spindles,  similar  to  stationary  engine  practice,  will  save  a  great 
deal  of  oil  on  all  such  locos  and  provide  more  uniform  lubrica- 
tion than  hydrostatic  lubricators. 

It  is  necessary  to  fix  the  mechanical  lubricator  with  heavy 
brackets  to  the  engine  frame,  and  take  every  precaution  that 
vibrations  from  the  engines  are  felt  by  the  lubricator  as  little  as 
possible.  The  oil  should  preferably  be  introduced  by  means  of 


392  PRACTICE  OF  LUBRICATION 

an  atomizer  (see  page  346)  into  the  steam  pipe  in  the  smoke  box, 
before  it  branches  off  to  each  cylinder. 

When  the  oil  is  thoroughly  atomized,  the  steam  lubricates 
both  valves,  cylinders  and  piston  rods,  so  that  there  is  no  need 
for  extra  lubrication  of  the  rods.  But  where  hydrostatic  lubri- 
cators or  tallow  cups  are  employed,  it  is  necessary  to  have  a  swab 
or  mop  for  the  rod  glands.  Suc'h  swabs  are  made  of  worsted  or 
cotton  (lamp  wicks),  plaited  and  formed  into  a  ring,  placed  round 
the  rod  and  held  in  position  by  the  gland  nuts;  they  are  prefer- 
ably enclosed  in  a  box  to  protect  them  from  dust  and  grit. 

Railway  Locomotives. — Coming  now  to  the  other  and  more  im- 
portant group  of  locos,  those  employed  in  regular  railway  service, 
whether  passenger  or  freight  service,  we  find  that  there  is  one 
condition  which  vitally  affects  the  lubrication  question,  namely, 
that  when  a  train  passes  a  down-gradient  portion  of  the  line,  the 
steam  is  practically  shut  off;  that  is,  the  engine  is  what  is  termed 
" drifting"  with  a  closed  throttle.  If  the  oil  under  these  condi- 
tions were  introduced  into  the  steam  pipe,  there  would  be  no 
steam  to  carry  it  into  the  valves  and  cylinders,  and  if  the  down- 
gradient  were  a  long  one  the  rubbing  surfaces  would  soon  be 
devoid  of  lubrication. 

During  periods  of  drifting  another  complication  occurs;  the 
valves  and  pistons  act  like  pumps  and  may  create  a  vacuum 
ranging  from  3  to  9  Ibs.  on  the  exhaust  side  which  sucks  ashes 
and  soot  into  the  cylinders  from  the  smoke  box.  These  impuri- 
ties adhere  to  the  cylinder  oil  and  may  form  very  objectionable 
crusty  deposits  in  the  valves,  passages  and  cylinders.  To  over- 
come this  difficulty,  good  practice  requires  either  that  the  driver 
shall  very  slightly  open  the  regulator  when  the  engine  is  drifting 
or  that  a  bye-pass  valve  (snifting  valve,  anti-vacuum  valve),  be 
provided,  which  automatically  admits  sufficient  steam  to  the  cylin- 
ders, so  as  to  kill  the  vacuum  and  prevent  the  entrance  of  soot 
and  ashes.  Some  snifting  valves  are  designed  to  admit  air  in- 
stead of  steam  or  air  and  steam.  This  practice  is  permissible 
for  saturated  steam,  but  with  superheated  steam  the  internal 
temperatures  are  so  high  that  the  air  immediately  oxidizes  the 
oil  and  causes  the  formation  of  sticky,  carbonaceous  deposits. 

It  will  now  be  realized  that  the  condition  of  " drifting"  neces- 
sitates the  oil  being  introduced  straight  into  the  valves  and 
cylinders.  With  saturated  steam  an  oil  feed  to  the  cylinder  is 
seldom  required,  but  with  superheated  steam  the  cylinder  feed 
cannot  be  dispensed  with. 

Speaking  generally,  75  per  cent,  of  the  oil  is  preferably  intro- 
duced into  the  valve  chest  and  25  per  cent,  into  the  cylinders. 


STEAM  ENGINES 


393 


As  to  the  method  of  introducing  the  oil,  there  can  be  no  question 
of  the  superiority  of  the  atomization  system  over  all  other  systems, 
and  for  superheated  steam  conditions  in  particular,  as  will  be 
explained  presently. 


D 


FIG.   157. — Hydrostatic  loco  lubricator. 


LUBRICATORS 

Both  hydrostatic  displacement  lubricators  and  mechanically 
operated  lubricators  are  employed  and  there  have  been  great 
controversies  of  opinion  as  to  their  respective 
merits. 

Hydrostatic  Lubricators. — These  lubricators  are 
fitted  in  the  cab,  as  shown  in  Fig.  157.  Steam 
is  admitted  to  the  lubricator,  condenses  in  the 
upper  part  of  same ;  by  gravity  displacement  the 
oil  is  forced  up  through  sight  feeds,  and  through 
long  feed  pipes  it  finally  reaches  the  valve 
chests  and  cylinders.  The  best  hydrostatic 
lubricators  admit  saturated  steam  to  the  feed 
pipes.  The  steam  keeps  the  pipes  hot  and  more 
or  less  emulsifies  the  oil,  so  that  it  is  readily 
atomized  in  passing  through  the  choke  plug  (C) 
always  fitted  before  the  oil  enters  the  engine. 
Fig.  158  shows  in  detail  such  a  choke  plug;  a 
valve  (1)  is  kept  constantly  vibrating  on  its  seat 
by  the  motion  of  the  engine;  the  mixture  of  oil 
and  saturated  steam  passes  through  fine  chan- 
nels and  cross  channels  in  the  valve,  or  between 
the  valve  and  its  seat;  the  churning  action 
thoroughly  atomizes  the  oil;  in  fact,  what  is 
produced  is  really  oily  steam — "Scotch  fog" — which  spreads 
quickly  over  the  internal  surfaces  and  forms  the  best  means  by 
which  the  oil  can  be  distributed. 

If  the  choke  plugs  were  absent,  the  difference  between  the 


394  PRACTICE  OF  LUBRICATION 

boiler  pressure  and  the  pressure  in  the  valve  chest  or  cylinder 
would  cause  waste  of  steam  through  the  oil  feed  pipes,  particu- 
larly when  drifting.  The  choke  plugs  are  therefore  required  for 
the  dual  purpose  of  checking  the  steam  flow  and  atomizing  the 
oil. 

When  applied  to  locos  employing  saturated  steam,  two  feeds, 
one  for  each  valve  chest,  will  suffice  for  most  high  pressure  en- 
gines; but  the  cylinders  in  large  engines  will  occasionally  be  better 
lubricated  if  they  are  lubricated  direct,  so  that  a  four-feed  lubri- 
cator is  required.  An  extra  feed  may  be  added  for  feeding  the 
air  pump  cylinder.  This  oil  feed  must  not  have  steam  admis- 
sion; the  oil  drops  through  a  sight  feed  and  gravitates  to  the  air 
cylinder. 

For  superheated  steam  conditions  hydrostatic  lubricators  are  al- 
most exclusively  used  in  the  United  States  and  Canada.  Some 
British  railways  are  also  using  them  and  getting  good  results. 

Although  the  lubricators  first  fitted  had  a  great  number  of 
feeds,  it  seems  now  to  be  an  established  fact,  that  for  all  two  cyl- 
inder engines  one  feed  into  each  valve  chest  (into  the  middle 
with  inside  steam  admission,  or  a  divided  feed  into  both  ends  with 
outside  steam  admission),  one  feed  into  each  cylinder,  one  feed 
divided  to  the  tail  rods,  and  one  feed  for  the  air  pump,  making  six 
feeds  in  all,  will  provide  proper  oil  distribution.  For  four  cylinder 
engines  more  feeds  are  required  and  it  is  advisable  to  fit  two  lubri- 
cators, one  for  either  side. 

In  the  United  States  the  oil  feeds  on  each  side  are  often  di- 
vided to  serve  both  valve  and  cylinder,  but  in  view  of  the  uncer- 
tainty as  to  which  path  the  oil  will  choose,  it  seems  better  practice 
to  feed  the  valve  and  cylinder  by  separate  feeds.  If  feeds  are  to 
be  divided  it  would  be  better  to  divide  one  feed  for  both  valves 
or  for  both  cylinders,  as  one  may  then  with  better  reason  expect  a 
fair  distribution  of  the  oil. 

The  division  of  feeds  must,  of  course,  be  done  after  the  oil  has 
passed  the  choke  plugs.  As  to  British  practice,  at  least  one  rail- 
way has  divided  the  cylinder  feed  without -any  apparent  ill  effects, 
but  the  feeds  to  the  valve  chests  have  not  to  the  author's  knowl- 
edge been  divided.  As  the  greatest  amount  of  oil  has  to  be  fed 
to  the  valves,  this  practice  appears  to  be  sound  and  preferable  to 
the  American  practice  of  dividing  the  feeds,  which  certainly  in- 
troduces an  element  of  uncertainty. 

Mechanically  Operated  Lubricators. — Mechanical  lubricators  have 
a  container  from  which  the  oil  purnps  draw  the  oil;  the  container, 
therefore,  is  not  under  pressure,  and  can  easily  and  quickly  be 
refilled  with  oil.  Filling  a  hydrostatic  lubricator  with  oil  is  more 


STEAM  ENGINES  395 

complicated,  as  the  water  first  "must  be  emptied  out,  and  there 
are  several  valves  to  look  after  every  time  to  ensure  correct  work- 
ing of  the  lubricator  when  starting  up  again.  Mechanical  lu- 
bricators start  feeding  as  soon  as  the  engine  starts,  and  stop 
feeding  with  the  engine,  so  that  no  oil  is  wasted  while  t^e  engine  is 
standing.  Hydrostatic  lubricators  must  have  their  oil  feeds 
started  about  ten  minutes  before  the  running,  and  they  keep  on 
feeding  while  the  engine  is  standing  or  running  slowly. 

Mechanical  lubricators  feed  the  oil  according  to  the  speed  of 
the  engine,  whereas  a  hydrostatic  lubricator  will  feed  approxi- 
mately the  same  amount  of  oil  whether  the  engine  goes  fast  or 
slow,  whether  on  an  uphill  or  downhill  gradient.  When  super- 
heated steam  was  first  introduced  on  the  Continent  mechanical 
lubricators  were  thought  necessary;  the  principle  of  atomization 
was  not  understood  or  appreciated  and  as  a  result  the  great 
majority  of  locomotives  in  Europe,  South  Africa,  India  and  in  the 
East  generally  are  fitted  with  mechanical  lubricators  without  any 
attempt  being  made  to  atomize  the  oil.  Numerous  troubles  with 
excessive  carbonization,  heavy  wear  and  friction,  are  recorded, 
too  numerous  to  be  disregarded. 

What  happens -is  that  the  oil  is  injected  unatomized  into  the 
valves  and  cylinders;  it  is  very  viscous  and  spreads  only  with 
difficulty;  the  oil  is  exposed  to  high  temperature,  to  the  oxidizing 
effect  of  hot  smoke  box  gases  and  boiler  impurities  and  to  con- 
tamination from  soot  and  ashes.  As  a  result,  particularly  if  the 
oil  consumption  is  liberal,  very  tenacious,  sticky  or  hard  carbon- 
aceous deposits  are  formed.  The  rubbing  surfaces  become  poorly 
lubricated  and  heavy  friction  and  wear  take  place.  Frequent 
cleaning  of  valves  and  cylinders  and  keeping  the  oil.  consumption 
as  low  as  possible  will  assist  in  preventing  trouble,  but  even 
with  the  best  possible  attention  to  these  points,  it  is  difficult  to 
ensure  perfect  lubrication. 

Of  course,  if  suitable  anti-vacuum  valves  are  fitted,  if  the  boiler 
water  is  of  good  quality,  and  priming  only  slight  or  absent,  it  is 
possible  to  get  good  results  with  mechanical  lubricators.  But 
results  in  practice  generally  fall  short  of  perfection,  and  it  is  under 
more  or  less  unfavorable  conditions  that  feeding  the  oil  unat- 
omized is  almost  sure  to  give  trouble.  The  fault  is  not  with  the 
mechanical  lubricators  themselves.  Stationary  practice  has  long 
since  proved  that  they  are  superior  to  and  more  economical  than 
hydrostatic  lubricators;  the  cause  of  most  carbonization  troubles 
is  simply  that  the  oil  is  not  atomized. 

The  good  results  obtained  with  hydrostatic  lubricators  under 
superheated  steam  conditions  have  proved  that  if  the  oil  is  intro- 


396 


PRACTICE  OF  LUBRICATION 


duccd  as  oil  fog,  saturated  steam  being  the  carrying  medium, 
it  has  the  effect  of  keeping  the  rubbing  surfaces  free  from  deposit. 
Whatever  impurities  may  be  drawn  into  the  engine  during  periods 
of  drifting  are  prevented  from  caking  and  expelled  through  the 
exhaust  when  steam  is  again  admitted. 

Experience  has  proved  that  perfect  atomization  is  imperative, 
if  carbon  deposits  are  to  be  avoided  with  superheated  steam. 

The  author  believes  he  was  the  first  to  suggest  the  combina- 
tion of  mechanical  lubricators  with  atomizing  boxes  (in  a  paper 
read  before  the  Institution  of  Locomotive  Engineers,  London,  on 
March  25th,  1915).  Fig.  159  shows  the  author's  design  (only 
patented  in  the  United  Kingdom),  which  has  proved  efficient  in 


L 


FIG.   159. — Thomen's  atomizer  arrangement. 

overcoming  carbonization  troubles.  The  feed  pipes  (1)  from  the 
mechanical  lubricator  (L)  discharge  oil  through  check  valves 
(2)  into  the  atomizer  box  (3),  shown  in  detail  in  Fig.  160.  Satu- 
rated steam  is  supplied  through  an  auxiliary  pipe  (4)  and  causes 
the  oil  to  be  preliminarily  atomized  through  the  sawslits  of  the 
atomizer  (5),  the  mixture  of  oil  and  saturated  steam  is  finally 
atomized  in  passing  through  the  choke  plug  (6) . 

It  will  thus  be  seen  that  the  steam  has  an  unobstructed  flow 
through  the  atomizer  box  and  each  feed  gets  its  fair  share  of  the 
steam  supply.  The  number  of  oil  feeds  required  is  exactly  the 
same  as  with  a  hydrostatic  lubricator.  Without  the  atomizer 
box,  piston  valves  require  two  oil  feeds,  one  for  each  end,  but  with 
the  atomizer  box  one  feed  for  the  centre,  or  one  feed  divided  for 
each  end,  as  the  case  may  be,  will  suffice. 


STEAM  ENGINES 


397 


The  combination  of  a  mechanical  lubricator  with  a  suitable 
atomizer  box,  in  the  author's  opinion,  offers  the  chief  advantages 
of  the  best  types  of  hydrostatic  lubricators  with  all  the  advantages 
of  mechanical  lubricators.  Only  those  oil  feeds  requiring 
to  be  atomized  -are  carried  to  the  atomizer  box.  Oil  feeds  for 
feeding  oil  under  pressure  to  the  axle  boxes  may  be  taken  from  .the 
lubricator,  and  if  need  be,  the  lubricator  can  be  made  with  two 
compartments,  so  that  a  separate  oil — axle  oil — can  be  used  for 
the  bearings,  and  cylinder  oil 
for  the  valves  and  cylinders. 
A  hydrostatic  lubricator  can, 
of  course,  not  be  arranged  to 
feed  pressure  oil  to  the  axle 
boxes. 

Mechanical  lubricators  are 
either  fitted  in  the  cab  near 
the  driver  or  on  the  framing 
near  the  main  points  of  lubri- 
cation. 

Motion  may  be  taken  from 
the  back  axle  or  from  one  of 
the  rods,  as  shown  in  Figs.  161 
and  162. 

The  check  valves  should  be 
designed  to  avoid  steam  leak- 
ing back,  and  the  vibration  calls 
for  special  care;  ordinary  mitre 
seated  valves  are  not  satisfac- 
tory. Fig.  163  shows  one  de- 
signed by  the  author,  which  has 
proved  efficient  under  trying 
conditions.  It  will  be  seen 

that  the  spring  operating  the  valve  is  on  the  oil  side  and  not 
exposed  to  the  steam;  the  valve  has  to  be  lifted  until  the 
cylindrical  part  is  above  the  seat  before  the  oil  will  be  discharged. 

When  oil  is  not  pumped  through  the  valve,  the  cylindrical 
portion  below  the  head  forms  an  effective  seal  against  the  en- 
trance of  steam  into  the  oil  pipe.  By  unscrewing  the  cleaning 
and  testing  plug  a  straight  passage  is  disclosed  for  cleaning  the 
oil  passage  leading  into  the  valve  or  cylinder.  This  plug  is 
screwed  back  when  testing  the  oil  feeds.  There  are  three  oil 
holes  below  the  head,  through  which  the  oil  will  exude. 

A  similar  type  of  check  valve  should  also  be  used  in  the  oil 
pipes  from  a  mechanical  lubricator  to  the  axle  boxes.  The 


FIG.  160. — Atomizer  box. 


398 


PRACTICE  OF  LUBRICATION 


check  valves  should  be  fitted  in  accessible  positions  and  as  near 
the  axle  boxes  as  possible. 


FIG.   161. — Back  axle  motion  for  mechanical  lubricator. 

Mechanical  lubricators  for  locomotives,  particularly  when 
placed  on  the  framing,  should  be  provided  with  a  steam  heating 
arrangement,  as,  if  the  cylinder  oil  becomes  very  thick  or  congeals, 


FIG.   162. — Rod  motion  for  mechanical  lubricator. 

the  oil  feeds  will  be  considerably  reduced  or  stop  altogether.     As 
to  placing  the  mechanical  lubricators,   they  are  undoubtedly 


STEAM  ENGINES 


309 


best  placed  in  Mir  nib,  where  the  lubricator  is  under  the  eye  of  the 
driver  and  stoker,  and  where  each  feed  to  each  part  of  the  engine 
can  be  properly  controlled  and  regulated.  This  also  makes  it 
possible  to  give  extra  oil  when  required  by  having  a  flushing 
handle  on  the  lubricator,  by  means  of  which  all  the  oil  feeds  can 
be  flushed.  Where  mechanical  lubricators  are  placed  on  the 
frame,  the  driver  cannot  control  and  watch  the  feeds  from  the  cab. 
If  one  of  the  feeds  gets  out  of  order,  he  will  not  be  able  to  recog- 
nize this  before  the  engine  gives  audible  notice  by  grunting,  or 
otherwise,  and  then  a  great  deal  of  damage  may  already  have 
been  done. 

It  is  felt  by  some  engineers  that  the  drivers  should  not  be 
allowed  to  adjust  the  feeds  when  once  set  by  an  expert  in  the 


Section  of  Valve  Stem 


Plan  of  Nut 
FIG.  163. — Locomotive  check  valve. 

running  shed,  or  during  a  couple  of  days'  service  on  the  road. 
The  lubricators  can  of  course  be  arranged  with  locked  adjust- 
ments, but  the  drivers  should  in  any  case  be  enabled  to  watch 
the  sight  feed  glasses  and  test  the  oil  feeds;  they  should  also  have 
access  to  the  suction  valves  and  to  the  flushing  arrangement. 

The  combination  of  a  mechanically  operated  lubricator  with 
an  atomizer  box  appears  to  be  the  best  solution  for  lubrication  of 
all  locomotives  in  those  outlying  countries  which  employ  native 
drivers,  as  it  is  desirable  that  the  lubrication  be  as  automatic 
and  foolproof  as  possible  and  the  control  largely  taken  out  of  the 
driver's  hands. 

For  those  countries  in  Europe  and  America  where  intelligent 
drivers  are  available,  the  hydrostatic  lubricator,  with  intelligent 
care,  is  capable  of  giving  good  service,  and  it  will  probably  con- 


400  PRACTICE  OF  LUBRICATION 

tinue  to  be  much  used  for  saturated  steam  conditions.  AK 
however  the  consumption  of  oil  with  mechanical  lubricators  can 
be  automatically  kept  nearer  the  actual  requirements  than  with 
the  hydrostatic  lubricator,  which  requires  frequent  and  intelli- 
gent adjustment  by  the  driver,  it  would  not  be  surprising  to  find 
the  mechanical  lubricator  gaining  in  favor  for  saturated  steam 
service.  For  superheated  steam  conditions  the  author  thinks 
that  the  development  will  certainly  be  in  favor  of  the  mechanical 
lubricator,  due  attention  being  paid  to  the  atomization  principle. 

LOCOMOTIVE  CYLINDER  OILS 

Most  locos  operate  with  rather  high  steam  pressures,  ranging 
from  140  Ibs.  to  225  Ibs.  per  square  inch. 

Most  works  locos  have  slide  valves,  but  many  railway  locos 
have  piston  valves.  Slide  valves  have  been  used  with  a  moderate 
degree  of  superheat,  but  for  high  superheat  piston  valves  are 
universally  adopted,  and  in  most  cases  also  tail  rods.  Piston 
rings  and  pistons  wear  much  better  when  tail  rods  are  fitted.  It 
is  not  considered  advisable  to  exceed  a  steam  temperature  of 
650°F. 

In  the  early  days  much  trouble  was  caused  by  the  growth  of 
cast  iron  when  exposed  to  superheat  temperatures.  For  a  long 
time  it  was  thought  that  the  cylinder  oil  was  to  blame  for  the 
excessive  wear  and  the  many  cracked  cylinders,  etc.,  but  even- 
tually the  swelling  was  found  due  to  the  combined  carbon  in  the 
iron.  A  more  suitable  cast  iron  was  discovered  and  solved  the 
difficulty,  and  many  railways  found  that  good  quality  filtered 
cylinder  oils,  which  they  had  previously  used  with  saturated 
steam,  served  quite  well  also  with  superheated  steam. 

Owing  to  the  wet  steam  conditions  often  met  with  in  locomo- 
tives, or  to  bad  water,  or.  to  the  necessity  of  keeping  an  extra 
high  water  level  before  negotiating  a  long  uphill  gradient,  ex- 
perience had  already  taught  some  railways  that  well  filtered 
green  cylinder  oils,  compounded  with  from  6  per  cent,  to  10  per 
cent,  of  acidless  tallow  oil,  gave  cleaner  and  better  lubrication  on 
a  much  reduced  feed  as  compared  with  dark  cylinder  oils,  whether 
straight  mineral  or  compounded.  The  majority  of  railways, 
however,  still  use  dark  cylinder  oils  for  all  conditions,  because 
they  are  lower  in  price  per  gallon  than  filtered  cylinder  oils. 

Experience  has  proved  that  locomotive  cylinder  oils  should 
certainly  be  compounded.  If  the  conditions  as  regards  priming, 
drawing  in  soot,  etc.,  are  not  too  trying,  dark  compounded  cylinder 
oils  will  give  a  reasonable  amount  of  satisfaction,  but  under 


STEAM  ENGINES  401 

unfavorable  conditions,  compounded,  filtered  cylinder  oils 
should  always  be  preferred,  as  they  maintain  the  valves  and 
cylinders  in  a  much  cleaner  condition,  which  is  worth  a  great 
deal  from  both  a  frictional  and  a  wear-and-tear  point  of  view. 

For  works  locos  fitted  with  poor  lubricators,  it  is  usually  a 
waste  of  money  to  use  filtered  cylinder  oils  and  dark  compounded 
oils  are  recommended.  The  use  of  tallow  should  be  discouraged, 
but  it  will  often  be  found  that  collieries  and  steel  works  buy  low 
priced,  straight  mineral,  dark  cylinder  oils,  that  the  locomotives 
use  the  oil  extravagantly,  and  yet  the  lubrication  is  so  poor,  that 
engine  drivers  get  tallow  (or  if  they  are  not  allowed  to  have  it, 
get  it  all  the  same)  to  keep  their  engines  quiet, 

The  bad  effects  of  using  tallow  are  mentioned  page  387.  Loco- 
motive cylinder  oils  should  obviously  have  good  setting  points, 
so  that  low  setting  point,  filtered  cylinder  oils  should  be  recom- 
mended which  will  flow  freely  in  the  lubricators  and  give  a  uni- 
form feed.  Compounded  filtered  cylinder  oils  will  also  lubri- 
cate the  air  pump  cylinder  satisfactorily,  if  fed  sparingly,  and 
very  little  oil  vapor  will  be  carried  over  with  the  compressed 
air  into  the  air  brake  system. 

The  consumption  of  cylinder  oil  required  for  full  lubrication 
varies  from  Y±  pint  to  \Y±  Pm^  per  100  miles,  according  to  the 
size  of  the  locomotive.  The  oil  consumption  for  the  air  pump 
varies  between  %  pint  and  J£  pint  per  100  miles  and  should  be 
kept  as  low  as  possible. 

Where  an  engine  has  a  long  continuous  run  to  make,  it  is  good 
policy  for  one  shift  of  driver  and  fireman  to  hand  the  engine 
over  to  the  next  shift  with  the  lubricator  filled  with  oil;  in  this 
way  control  of  the  various  drivers'  oil  consumption  is  made  quite 
easy. 

LUBRICATION  CHART  No.  11 

FOR  Locos 

Works  Locos. l 

Small  locos Cylinder  Oil  No.  2  D.M.C. 

Larger  locos Cylinder  Oil  No.  3  D.M.C. 

Railway  Locos. 

Saturated  steam Cylinder  Oil  No.  3  F.M.C.  or  No.  3  D.M.C. 

Superheated  steam Cylinder  Oil  No.  3  F.M.C. 

NOTE.  l — For  very  wet  steam,  the  same  grades  are  recommended,  but  with 
10  per  cent,  of  compound. 


CHAPTER  XXV 
BLOWING  ENGINES  AND  AIR  COMPRESSORS 

Compressed  Air. — Compressed  air  is  used  for  a  variety  of 
purposes — for  supplying  blowing  air  to  blast  furnaces  and  Bes- 
semer converters;  for  operating  pneumatic  tools,  such  as  pneu- 
matic hammers,  drills,  riveters,  etc.,  as  used  in  engineering 
works,  boiler  shops,  foundries,  forge  shops,  shipyards,  docks, 
and  bridge  building;  for  rock  drills  used  in  mines  and  quarries; 
for  operating  underground  machinery  in  collieries,  and  for  sink- 
ing tunnels  and  shafts.  It  is  also  used  for  operating  different 
types  of  lifting  and  hoisting  gear,  railway  car  brakes,  electro- 
pneumatic  signals,  and  pneumatic-tube  carrying  service;  for 
pumping  water;  for  lifting  and  conveying  liquids  in  breweries, 
distilleries  and  chemical  works;  for  aerating  oils  in  large  edible 
oil  refineries  and  for  spraying  paint. 

Compressed  air  is  employed  for  starting  gas  engines  and  other 
internal  combustion  engines;  also  for  injecting  and  atomizing 
fuel  oil  under  furnaces  or  in  Diesel  engines.  Very  highly  com- 
pressed air  is  used  for  producing  oxygen  and  liquid  air. 

TYPES  OF  BLOWING  ENGINES  AND  AIR  COMPRESSORS 

Blowing  engines  supply  large  volumes  of  air  at  low  pressure. 
Blast  furnaces  require  air  at  10  to  25  pounds  per  square  inch; 
Bessemer  converters  require  air  at  20  to  30  pounds  per  square 
inch. 

Blowing  engines  operate  at  low  speeds,  from  30  to  7p  R.P.M. 
and  are  single  stage  machines;  they  are  operated  by  either  steam 
or  gas  engines;  the  gas  engines  are  nearly  always  horizontal,  two- 
stroke  cycle  engines,  driving  the  air  cylinder  tandem  fashion. 
When  driving  the  blowing  engines  by  steam  engines,  the  steam 
and  air  cylinders  are  also  usually  placed  in  tandem.  In  hori- 
zontal blowing  engines  the  piston  nearly  always  has  a  tail  rod. 
When  the  tail-rod  support  is  not  present,  the  whole  of  the  weight 
of  the  piston  is  sliding  on  the  bottom  of  the  cylinder,  demanding 
the  use  of|heavy  bodied  oils. 

Air  compressors  compress  air  to  high  pressures.  Colliery  air 
compressors  compress  large  volumes  of  air  to  a  pressure  of  from 

402 


BLOWING  ENGINES  AND  AIR  COMPRESSORS 


403 


00  to  80  pounds  per  square  inch;  they  are  sometimes  single-stage 
compressors  but  more  frequently  they  are  two-stage. 

The  majority  of  compressors  used  for  a  variety  of  purposes, 
as  enumerated  above,  compress  air  to  a  pressure  of  from  80  to 
120  pounds  per  square  inch.  Small  compressors  operating  at  a 
high  speed,  are  frequently  single-stage  machines  up  to  a  delivery 
pressure  of  120  pounds  per  square  inch.  Large  compressors  are 
nearly  always  two-stage  machines  when  the  air  pressure  exceeds 
70  pounds  per  square  inch.  Small  or  medium  size  compressors 
used  in  connection  with  semi-Diesel  oil  engines  compress  air  to 
about  400  to  450  pounds  per  square  inch  and  are  two-stage 
machines. 

Air  compressors  used  in  connection  with  Diesel  engines  com- 
press air  to  a  pressure  of  about  1000  pounds  per  square  inch. 
(See  Diesel  Engines,  page  525.) 

Air  compressors  when  used  in  connection  with  the  production 
of  oxygen  compress  air  to  a  pressure  of  2000  pounds  per  square 
inch  and  are  usually  four-stage  machines.  The  types  used  for 
charging  torpedoes  compress  air  to  3000  pounds  per  square 
inch  and  are  usually  four-  or  five-stage  machines. 

Horizontal  air  compressors  are  usually  steam  driven  with  steam 
and  air  cylinders  in  tandem.  Vertical  air  compressors  may  be 
driven  by  steam,  by  an  electric  motor,  or  by  belt  from  a  trans- 
mission shaft. 

TABLE  No.  20 
CLASSIFICATION  OF  AIR  COMPRESSORS  AND  BLOWING  ENGINES 


Air  pressure, 
Ibs. 
per.  sq.  inch 

R.P:M. 

Single  or  double 
acting 

Blowing  engines 
Blast  furnace 

10-25      \ 

20-30     J 
Diesel  engine 

Up  to  120  1 
Up  to  450  J 

Up  to  120  \ 
Up  to  450  J 

jUp  to  70    \ 
jUp  to  150  J 

Up  to  70    \ 
Up  to  150  J 

30-70 

-, 
compres 

300-500 
150-250 
60-360 
40-150 

Double  acting. 

sors)  j 
J 

Single  acting. 
Double  acting. 
Usually  single  acting. 
Double  acting. 

Bessemer   converters 

Air  compressors  (exclusive  of 
Small  vertical 
Single-stage  .... 

Two-stage 

Smatt  horizontal 
Single-stage 

Two-stage  

Large  vertical 
Single-stage 

Two-stage  

Large  horizontal 
Single-stage 

Two-stage  

404  PRACTICE  OF  LUBRICATION 

Blowing  engines,  and  air  compressors  may  be  classified  as 
shown  in  Table  No.  20.  A  compressor,  whether  it  be  a  single- 
or  a  two-stage  machine,  is  classified  as  small  or  large,  according 
to  whether  the  volume  of  free  air  entering  the  machine  is  less  or 
more  than  1000  cubic  feet  per  minute. 

AIR  COOLING  AND  FILTRATION 

Cooling. — As  blowing  engines  only  compress  the  air  to  low 
pressure,  the  amount  of  heat  produced  is  not  very  great,  so  that 
blowing  engine  cylinders  are  practically  never  water  cooled. 
In  air  compressors  which  compress  the  air  to  higher  pressures 
and  which  operate  at  much  higher  speeds,  the  heat  of  compres- 
sion is  great,  particularly  around  the  outlet  valves,  through  which 
the  hot  compressed  air  is  discharged. 

Cooling  of  the  air  compressor  cylinder  therefore  becomes  neces- 
sary, and  under  severe  conditions,  attempts  are  frequently  made 
to  cool  also  the  parts  in  close  proximity  to  the  outlet  valves. 
Without  adequate  cooling,  the  temperature  would  rise,  causing 
unequal  expansion  and  distortion  of  the  compressor  cylinder, 
valves  and  valve  seats.  The  lubricating  oil  film  between  the 
piston  rings,  and  cylinder  walls  would  be  thinned  out,  losing  its 
sealing  power,  and  the  compressed  air  would  leak  past  the  piston. 
The  discharge  valves  would  not  keep  air  tight  (distortion  due  to 
heat)  resulting  in  wire  drawing  and  recompression  of  the  air, 
charring  of  the  lubricating  oil,  excessive  carbonization,  friction, 
and  wear. 

If  air  at  a  temperature  of  60°F.  is  compressed  in  a  one-stage 
compressor  to  100  pounds  per  square  inch,  its  temperature  will 
theoretically  increase  to  485°F. ;  under  actual  working  conditions 
the  temperature  will,  however,  be  lower,  due  to  the  cooling  effect 
of  the  cooling  water  jacket. 

When  air  is  compressed  at  a  temperature  of  60°F.  to  100 
pounds  pressure  in  a  two-stage  compressor,  compressing  the 
air  to,  say,  35  pounds  pressure  per  square  inch  in  the  low  pressure 
cylinder,  and  cooling  the  air  in  an  inter-cooler,  the  temperature 
of  the  air  leaving  the  high  pressure  cylinder  will  be  considerably 
lower,  from  200°F.  to  250°F.,  only  in  rare  cases  going  as  high  as 
300°F.  This  example  shows  the  value,  as  far  as  lubrication  is 
concerned,  of  compressing  air  in  several  stages  when  the  final 
air  pressure  required  is  high. 

The  effect  of  the  lower  temperature  is  also  that  it  takes  con- 
siderably less  power  to  compress  the  air  (20  per  cent,  less  in  the 


BLOWING  ENGINES  AND  AIR  COMPRESSORS 


405 


case  just  mentioned),  this  forming  another  strong  reason  in  favor 
of  multiple-stage  compressors. 

The  air  is  frequently  cooled  in  an  after-cooler  when  leaving  the 
compressor.  The  air  in  cooling  will  deposit  its  surplus  moisture 
and  a  large  portion  of  the  oil,  which  is  thus  prevented  from  reach- 
ing the  receiver. 

Occasionally  a  separator  partly  filled  with  water  is  fitted  in 
series  with  or  in  place  of  the  after-cooler  (Fig.  164).  The  water 
assists  in  extracting  dust  and  excess  water  from  the  air.  A  feed 
pipe  and  blow-off  cock  are  fitted,  as  indicated,  so  that  the  water 
can  be  changed  under  pressure.  Accumulated  oil  can  be  blown 


1.  Air  inlet. 

2.  Air  outlet. 

3.  Waterjflevel  blow  off  cock. 

4.  Bottom  blow  off  cock. 

5.  Water  feed  pipe  connection. 


FIG.   164. — Air  purifier. 


out  from  time  to  time  through  a  scum  cock.     This  may  also  be 
connected  to  an  automatic  trap. 

Filtration. — Where  the  air  is  charged  with  dust,  a  strainer  or 
filter  should  be  fitted.  It  may  be  made  of  screens  of  wire  gauze 
and  may  contain  cotton  wool  or  fibre,  in  order  ro  retain  the 
impurities.  If  the  air  is  dirty  and  impurities  reach  the  compres- 
sor, the  impurities  will  adhere  and  cling  to  the  oil  film,  baking 
together  into  carbonaceous  deposits.  The  intake  air  should 
therefore  be  taken  from  outside  the  compressor  room  and  from 
as  clean  a  place  as  possible.  The  intake  air  may  be  freed  from 
dust  by  passing  through  a  container  filled  with  3-inch  stones, 
coated  with  thick  refuse  oil  and  closed  with  grids  to  keep  in  the 
stones.  The  container  and  stones  should  be  cleaned  once  or 
twice  a  year  and  the  stones  recoated  with  oil. 


406  PRACTICE  OF  LUBRICATION 

METHODS  OF  LUBRICATION 

Feeding  Oil  into  Air  Intake.— In  small  and  medium  size  air  com- 
pressors, oil  is  occasionally  introduced  into  the  flow  of  air  passing- 
through  the  air  inlet  pipe.  The  air  atomizes  and  carries  the  oil 
in  the  form  of  a  fine  spray  into  the  cylinder.  The  oil  is  cold  and 
the  air  is  not  a  good  carrying  medium  for  oil,  so  that  frequently 
this  practice  does  not  give  the  best  results. 

In  horizontal  air  compressors  or  blowing  engines,  if  the  oil  be 
introduced  into  the  air  intake,  it  will  with  difficulty  reach  the 
top  portion  of  the  piston,  as  it  arrives  there  only  by  slowly 
wedging  its  way  up  around  the  sides  of  the  piston.  This  practice 
is  therefore  uneconomical,  as  a  large  quantity  of  oil  has  to  be 
fed  in  order  .to  insure  oil  reaching  the  top  of  the  piston. 

In  vertical  air  compressors  the  practice  of  feeding  oil  into  the 
air  inlet  pipe  has  a  greater  chance  of  distributing  the  oil  than 
in  horizontal  air  compressors,  but  it  is  also  here  rather  wasteful 
and  not  conducive  to  the  best  results. 

Feeding  Oil  Direct. — Generally  speaking,  it  is  better  to  feed  the 
oil  direct  to  the  frictional  surfaces,  feeding  it  sparingly  and  uni- 
formly. In  horizontal  blowing  engine  or  air  compressor  cylin- 
ders, the  oil  is  introduced  at  the  centre  of  the  cylinder,  either  at 
one  point,  at  the  top,  or  at  three  points,  one  at  the  top  and  two 
lower  down.  It  will  then  gradually  work  its  way  around  the 
piston  and  form  a  complete  sealing  and  lubricating  film. 

In  vertical  cylinders,  oil  is  introduced  at  two  points,  front  and 
back,  or  at  several  points  evenly  spaced  around  the  cylinder. 
Each  oil  inlet  to  the  cylinder  should  preferably  be  fed  by  a  sepa- 
rate oil  pump,  so  that  each  feed  can  be  controlled  with  certainty. 
If  one  oil  pump  supplies  several  oil  inlets  to  the  cylinder,  the  oil 
will  take  the  path  of  least  resistance,  and  will  not  feed 
through  those  inlets  which  have  become  choked  with  dirt  or 
deposit. 

Splash  irom  Crank  Chamber. — In  vertical  enclosed  high  speed 
air  compressors  where  the  external  moving  parts  are  enclosed  in  a 
crank  chamber,  and  lubricated  either  by  means  of  the  splash 
system  of  lubrication  or  the  force  feed  circulation  system,  the 
oil  is  either  splashed  or  forced  to  all  parts  requiring  lubrication, 
so  that  no  separate  oiling  of  the  piston  is  required.  On  the 
contrary,  the  difficulty  is  usually  to  prevent  too  much  oil  from 
passing  the  piston  rings  and  getting  to  the  top  of  the  piston, 
where  the  oil,  exposed  to  the  high  temperature  and]?oxidizing 
effect  of  the  air,  will  in  time  bake  into  a  carbonaceous  deposit. 

The  presence  of  a  large  amount  of  oil  in  the  air  also  produces  a 


BLOWING  ENGINES  AND  AIR  COMPRESSORS          407 
* 

similar  deposit  on  the  discharge  valves,  frequently  causing  great 
trouble. 

VALVE  LUBRICATION 

Grid  valves  have  large  sliding  surfaces  which  must  be  lubricated 
direct,  by  introducing  the  oil  at  several  points,  sparingly  and 
uniformly,  the  oil  gradually  finding  its  way  all  over  the  sliding 
surfaces. 

Flap  valves  have  hinges  which  must  be  oiled,  sparingly  and 
uniformly,  the  oil  being  introduced  through  feed  pipes  passing 
through  the  cylinder  head. 

Leather  disc  valves  need  no  lubrication,  but  the  leathers  must 
be  kept  flexible  and  in  good  order  by  occasional  application  of 
neatsfoot  oil  or  lard  oil. 

Corliss  valves  (only  used  as  suction  valves)  need  lubrication, 
particularly  at  their  ends  where  the  valves  have  their  bearing 
surfaces;  the  oil  must  be  introduced  direct  to  these  ends,  spar- 
ingly and  uniformly.  The  practice  of  fitting  grease  cups  supply- 
ing grease  to  the  valve  ends  is  not  to  be  recommended,  partly 
because  grease  spreads  only  with  difficulty  over  the  rubbing  sur- 
faces and  partly  because  it  bakes  together  with  the  impurities  in 
the  intake  air  into  a  pasty,  sludgy  deposit,  causing  excessive 
friction  and  wear;  some  of  the  grease  will  reach  the  valve  chamber, 
and  even  the  cylinder,  where  it  will  bake  together  with  impurities 
and  cause  an  objectionable  varnish-like  deposit. 

Poppet  valves  usually  get  sufficient  lubrication  from  the  oil 
in  the  air. 

Plate  or  disc  valves  require  no  lubrication. 

Bucket  valves  themselves  require  no  lubrication,  but  their 
spindles  must  be  sparingly  lubricated. 

Lubrication  of  external  parts  is  by  means  of  splash  oiling  or 
force  feed  circulation  in  the  case  of  all  high  speed  enclosed  type 
air  compressors;  in  open  type  air  compressors  any  of  the  many 
systems  employed  for  bearing  lubrication  may  be  employed  and 
do  not  call  for  an}/  special  comments. 

With  splash  oiling  it  is  very  important  that  the  correct  oil 
level  be  maintained,  so  that  an  adjustable  overflow  should  prefer- 
ably be  fitted  to  the  crank  chamber. 

Owing  to  the  high  efficiency  of  the  force  feed  circulation  oiling 
system  and  to  the  vertical  construction,  vertical  afr  compressors 
may  operate  at  much  higher  speeds  than  horizontal  air 
compressors,  as  indicated  in  Table  No.  20,  page  403. 


408 


PRACTICE  OF  LUBRICATION 


Care  should  be  taken  that  the  piston  rings  and  oil  scrapers  on 
the  lower  part  of  the  trunk  pistons  be  pegged  and  in  good  order; 
they  will  then  wear  to  a  fit  with  the  cylinder  and  keep  oil  tight  and 
compression  tight. 

In  vertical  enclosed  type  air  compressors  employing  the  force 
feed  circulation  oiling  system,  the  oil  pressure  should  not  exceed 
5  to  15  pounds.  With  excessive  oil  pressure  too  much  oil  spray 
is  formed  and  too  much  oil  is  inclined  to  pass  the  pistons,  particu- 
larly so  when  the  governor  operates  by  throttling  the  intake  air, 
as  the  high  vacuum  created  in  the  cylinders  tends  to  draw  the 
oil  past  the  piston  rings. 

Splash  guards  fitted  over  the  crank  webs  and  pegging  the  piston 
rings  will  assist  materially  in  reducing  the  oil  consumption. 


LUBRICATORS 

Usually  sight  feed  drop  oilers  or  mechanically  operated  force 
feed  lubricators  are  employed. 

Sight  feed  drop  oilers  are  subject  to  considerable  variation  in 
oil  feed.  If  the  containers  are  full,  they  will  feed,  say,  three 
drops  per  minute;  when  they  are  nearly 
empty,  they  will  feed,  say,  one  drop  per 
minute.  They  also  vary  with  the  tempera- 
ture of  the  oil,  the  feed  increasing  when  the 
oil  gets  warm  and  thin;  in  addition,  when 
they  are  adjusted  to  feed  a  very  small 
amount  of  oil,  which  is  required  in  air  com- 
pressor practice,  grit  or  dirt  may  easily 
choke  the  needle  valve  controlling  the  oil 
feed. 

When  a  sight  feed  drop  oiler  is  to  feed 
oil  direct  into  the  cylinder  it  must  be  en- 
closed, so  that  it  will  feed  notwithstanding 
the  varying  back  pressure.  (See  Fig.  165.)  A  pressure  equaliz- 
ing pipe  connects  the  sight  feed  chamber  with  the  space  above 
the  oil  in  the  oil  container. 

The  oil  should  preferably  be  fed  by  means  of  a  reliable  mechan- 
ically operated  lubricator,  having  positive  visible  oil  feeds,  and  of 
such  construction  that  it  will  feed  a  minimum  quantity  of  oil 
with  the  greatest  regularity  and  precision.  The  oil  feeds,  once 
adjusted,  should  remain  absolutely  constant,  independent  of  the 
oil  level  in  the  container  and  independent  of  the  viscosity  of 
the  oil. 


FIG.   165. 


BLOWING  ENGINES  AND  AIR  COMPRESSORS  409 

OIL-DEPOSITS  AND  EXPLOSIONS 

All  open  type  compressors  are  so  constructed  that  an  oil  spe- 
cially chosen  to  suit  the  air  compressor  requirements  can  be  em- 
ployed and  applied  quite  independently  of  the  oil  used  for  the 
external  moving  parts.  In  enclosed  type  air  compressors  the 
same  oil  must  be  used  for  air  cylinders  and  bearings  and  both 
requirements  must  be  given  consideration.  The  chief  trouble 
in  air  compressor  lubrication  is  the  formation  of  carbon  deposits 
which  may  and  may  not  bring  about  explosions  or  fires. 

Deposits. — Deposits  may  form  on  the  pistons,  piston  rings, 
valves,  in  the  discharge  chambers,  pipes,  coolers  and  receivers. 

Deposit  on  the  piston  rings  may  fill  up  the  grooves  and  make 
them  inoperative,  causing  heavy  friction  and  wear,  and  air  leak- 
age past  the  piston. 

Deposit  on  the  discharge  valves  and  valve  seats  prevents  the 
valves  from  seating  properly;  the  hot  compressed  air  will  leak 
back  into  the  cylinder  on  the  suction  stroke;  recompression 
will  cause  the  temperature  of  the  discharged  air  to  increase  above 
normal. 

If  a  discharge  valve  sticks  in  a  partially  open  position,  the  air 
is  wiredrawn  and  recompressed  continuously;  the  hot  air  heats 
the  valve  and  the  temperature  may  easily  rise  to  700°F.  or  more, 
which  is  the  spontaneous  ignition  temperature  of  average  quality 
oil.  The  deposit  now  becomes  incandescent,  and  accumulated 
oil  will  vaporize  and  burn  or  explode.  Most  explosions  in  colliery 
compressors  appear  to  be  caused  by  discharge  valves  sticking. 

Deposit  on  the  suction  valve  causes  leakage  on  the  compression 
stroke,  and  wiredrawing  of  the  air  causes  heating  of  the  valve 
and  seat. 

Deposits  in  the  discharge  pipe  restrict  the  opening;  cases  have 
been  known  where  they  have  been  almost  choked,  causing  abnor- 
mally high  pressure  and  temperature  of  the  discharge  air. 

Deposits  may  develop  due  to  impurities  in  the  intake  air, 
inefficient  cooling,  too  warm  intake  air,  too  much  oil,  or  unsuit- 
able oil. 

Impurities  in  Intake  Air. — When  air  compressors  operate  in 
dusty  surroundings  as  in  collieries  and  quarries,  the  dust  fre- 
quently brings  about  deposits  inside  the  compressor  cylinders, 
valves,  etc.,  unless  the  intake  air  is  filtered. 

In  one  colliery  several  explosions  had  occurred  in  one  of  their 
compressors,  but  when  it  was  arranged  to  filter  the  intake  air 
(which  revealed  how  very  dirty  the  air  was)  no  further  explosions 
took  place. 


410  PRACTICE  OF  LUBRICATION 

In  another  colliery  an  electrically  driven  compressor  was 
placed  down  a  pit  in  a  place  where  the  coal  trains  passed  by, 
with  the  result  that  the  pistons  and  valves  were  constantly 
choking  up  with  deposit,  and  heavy  wear  took  place.  A  sample 
of  deposit  taken  from  the  valves  showed  the  following  analysis: 

Moisture Traces 

Oil 26.0  per  cent. 

Volatile  matter  (coal  dust  and  oil  carbon) ....  54.0  per  cent. 

Fixed  carbon  and  oxides  of  silica 0.9  per  cent. 

Iron  oxides  (chiefly  wear) 18.1  per  cent. 

Balance — undetermined 1.1  per  cent. 

100.0  per  cent. 


A  filter  was  then  installed  and  the  compressor  kept  very  much 
cleaner. 

Inefficient  cooling  may  be  due  to  furring  up  of  the  water 
jackets;  the  result  is  that  the  oil  is  charred  and  bakes  together 
with  metallic  wearings  from  the  piston,  piston  rings,  and  cylinder. 

Neglect  on  the  part  of  the  attendant  in  not  turning  on  the 
cooling  water  supply  when  starting  the  compressor  has  been 
responsible  for  such  deposits  and  even  explosions  have  taken 
place. 

Warm  Intake  Air. — The  warmer  the  intake  air  the  hotter  will 
be  the  discharge  air,  the  results  being  similar  to  those  of  inefficient 
cooling.  A  certain  difference  in  temperature  of  the  intake  air 
means  a  much  bigger  difference  in  the  temperature  of  the  dis- 
charge air,  which  emphasizes  the  desirability  of  having  the  intake 
air  as  cool  as  possible. 

Too  Much  Oil. — Air  compressors  require  very  little  oil  for 
lubrication  because  the  oil  remains  a  long  time  once  inside  the 
compressor;  there  is  no  steam  to  wash  the  oil  away  as  in  steam 
engines,  and  no  high  temperatures  to  burn  it  away  as  in  internal 
combustion  engines. 

Air  compressors  can  rarely  get  little  enough  oil;  the  excess  oil 
remaining  on  the  piston  or  valves  often  gets  charred  into  a  hard 
carbonaceous  deposit. 

Unsuitable  Oil. — The  character  of  the  oil  itself  greatly  influences 
the  character  and  amount  of  carbon  deposit  formed. 

Pale  oils  containing  chiefly  saturated  hydrocarbons  —  naph- 
thenes  or  paraffins — produce  less  oil  carbon  than  such  dark 
colored  oils  which  contain  types  of  hydrocarbons  easily  decom- 
posed by  oxidation. 

Distilled  oils  produce  much  less  deposit  than  undistilled  oils. 
Exposed  to  high  temperatures  they  distil  away  almost  completely, 


BLOWING  ENGINES  AND  AIR  COMPRESSORS          411 

leaving  comparatively  little  residue  behind;  whereas  undistilled 
oils,  exposed  to  high  temperatures  only  distil  partially,  leaving  a 
spongy,  carbonaceous  residue  behind.  Dark  cylinder  oils 
leave  much  more  residue  than  filtered  cylinder  oils  and  ought 
never  to  be  used  for  air  compressor  service. 

As  regards  fixed  oil,  it  is  obvious  that  semi-drying  or  drying 
oils  cannot  be  permitted  as  an  ingredient  in  air  compressor  oils,  but 
the  presence  of  a  small  percentage,  say,  3  per  cent,  of  non-drying 
animal  oil  is  not  detrimental  for  air  compressor  lubrication;  in 
fac  ,  it  has  proved  a  distinct  advantage  in  multiple-stage  high 
pressure  air  compressors  where  the  air  in  the  higher  stages  is  wet 
(see  Diesel  Compressors,  page  525).  For  low  or  moderate 
pressure  compressors,  when  the  air  is  comparatively  dry,  the 
admixture  of  fixed  oil  is  unnecessary. 

Oils  too  heavy  in  viscosity  are  largely  responsible  for  deposits; 
the  dust  and  dirt  in  the  air  adhere  to  the  sluggish  oil  and  form  a 
black  pasty  deposit. 

The  cry  for  high  flash  point  compressor  oils  which  comes  up 
now  and  again  after  compressor  explosions  in  mines,  usually 
meets  with  a  far  too  ready  response.  High  flash  point  means 
high  viscosity  (large  percentage  of  filtered  cylinder  stock  in  the 
oil)  and  this  inevitably  means  more  trouble  with  carbon  deposit 
than  ever. 

In  colliery  compressors  using  air  compressor  oils  with  a  flash 
point  of  over  500°F.  (steam  cylinder  oils)  the  coal  dust  bakes 
together  with  the  oil  and  presents  a  smooth  glossy  surface,  due 
to  the  pitch  and  tar  contained  in  the  coal  dust.  Such  high  flash 
point  oils  have  one  virtue,  however,  in  that  they  do  not  give  off 
much  vapor  exposed  to  the  normal  air  temperatures  in  an  air 
compressor.  Their  use  is  therefore  justified,  in  fact  may  be 
quite  necessary,  where  lower  flash  point  oils  give  off  so  much 
vapor  that  they  affect  the  throats  and  lungs  of  the  workmen 
in  tunnel  work,  collieries  below  ground,  air  worked  machinery 
in  confined  spaces,  etc.  For  such  conditions,  reasonably  low 
viscosity  filtered  cylinder  oils  should  be  employed.  The  flash 
point  is  no  safe  criterion  as  to  the  amount  of  vapor  given  off  below 
the  flash  point.  Speaking  generally,  high  viscosity  oils  act 
sluggishly  and  are  inclined  to  retain  much  of  the  dust,  particularly 
on  the  discharge  valves,  where  the  maximum  temperature  exists. 
When  such  oils  are  used,  and  the  air  is  dirty,  it  must  be  filtered 
and  the  compressor  pipes  and  receivers  should  be  frequently 
examined  and  cleaned,  so  that  notwithstanding  the  sluggish  oil, 
the  danger  of  explosions  may  be  avoided. 

Low  viscosity  oils  assist  in  maintaining  the  compressor  in  a 


412  PRACTICE  OF  LUBRICATION 

clean  condition,  notwithstanding  dirty  surroundings;  the  dii4t 
which  gets  in  is  kept  moving,  is  largely  passed  through  the  com- 
pressor and  out  of  the  discharge  valve  into  the  discharge  pipe, 
after-cooler  and  receiver. 

Soap  and  water  are  excellent  for  cleaning  purposes,  but  the 
use  of  soap  and  water  as  a  lubricant  does  not  dissolve  existing 
deposits;  in  fact,  more  deposit  is  formed,  as  the  water  evaporates 
away.  In  one  case  a  2  inch  deposit  (which  ignited  at  400°F.) 
was  formed  inside  the  discharge  pipe  of  a  compressor,  lubricated 
entirely  by  soap  and  water.  Explosions  have  been  reported  to 
have  occurred  when  soap  and  water  have  been  exclusively  used 
for  lubrication,  but  the  author  has  no  personal  knowledge .  of 
any  such  cases. 

EXPLOSIONS 

We  have  seen  several  reasons  for  the  production  of  abnormally 
high  temperatures.  The  heat  emanates  chiefly  from  the  dis- 
charge valve  or  valves,  and  it  is  probably  safe  to  say  that  fires 
or  explosions  originate  at  or  near  the  discharge  valve  chamber. 

Exposed  to  high  temperature  the  accumulated  oil  or  oily  deposit 
will  begin  to  emit  vapor  at  120°F.  to  150°F.  below  the  open 
flash  point  of  the  oil.  As  the  temperature  increases  the  oil  will 
vaporize  more  vigorously,  and  when  the  temperature  is  well 
above  the  flash  point,  the  mixture  of  oil  vapor  and  air  may 
easily  accumulate  in  or  near  the  discharge  valve  chamber  and 
be  in  the  right  condition  to  explode.  Perhaps  a  small  piece  of 
deposit  on  the  discharge  valve  commences  to  glow  sufficiently 
to  fire  the  mixture.  A  temperature  of  about  700°F.  is  sufficient 
to  ignite  the  oil  vapors  spontaneously,  and  a  fire  or  explosion 
follows. 

Experience  seems  to  show  that  in  large  moderate  pressure 
compressors  explosions  do  not  occur  if  the  intake  air  is  filtered 
or  if  deposits  are  not  allowed  to  accumulate  in  too  great  quanti- 
ties. When  there  are  no  deposits  there  can  be  no  fire,  therefore 
no  explosions.  The  amount  of  oil  used  for  lubrication  in  large 
compressors  is  so  small  compared  with  the  large  volume  of  air 
passing  through  the  compressor  that  the  oil  vapors  formed, 
even  under  high  temperature  conditions,  are  so  diluted  that  they 
cannot  explode.  If  an  explosion  occurs,  it  is  frequently  too 
weak  to  burst  pipings  or  receivers. 

The  high  temperature  may,  of  course,  ignite  accumulated  oily 
deposits  in  the  discharge  pipe,  in  which  case  the  fire  will  spread 
slowly  to  the  receivers.  The  burning  deposit  may  make  the 
receiver  walls  red  hot,  so  that  they  burst,  being  unable  to  with- 
stand the  normal  receiver  pressure. 


BLOWING  ENGINES  AND  AIR  COMPRESSORS  413 

In  one  typical  case  of  a  colliery  compressor  the  accumulation 
of  coal  dust  and  oil  in  pipes  and  receiver  had  not  been  cleaned 
out  for  two  years;  there  was  a  weak  explosion  and  the  deposit 
burned  for  a  considerable  time,  causing  men  in  the  pit  operating 
coal  cutters  to  cease  work  owing  to  the  obnoxious  fumes  in  the 
compressed  air. 

In  another  case,  a  leaking  joint  on  the  discharge  pipe  close  to 
the  compressor  had  been  " cured"  by  driving  a  piece  of  wood  into 
the  joint.  The  point  of  the  wood  protruded  inside  the  pipe  and 
ignited  spontaneously,  due  to  abnormally  hot  discharge  air. 
The  fire  spread  to  the  receiver,  and  the  latter  being  opened  up 
three  cwts.  of  deposit  accumulated  over  seven  years  were  removed, 
or  rather  what  remained  after  most  of  the  combustible  matter 
had  burned  away. 

If  the  dust,  which  together  with  the  oil  forms  the  deposit,  is 
itself  inflammable,  such  as  coal  dust,  the  danger  of  the  deposit 
taking  fire  is,  of  course,  greater  than  where  it  consists  of  non- 
inflammable  ingredients,  such  as  fine  sand  and  dust  in  quarries, 
iron  mines,  etc. 

In  multiple  stage  high  pressure  compressors,  where  the  volume 
of  air  discharged  is  comparatively  small,  the  amount  of  oil  used 
for  lubrication  and  intermingled  with  the  air,  is  appreciable, 
and  under  conditions  of  abnormal  temperatures,  explosive  mix- 
tures of  oil  vapor  and  air  are  formed,  which  will  bring  about 
violent  explosions,  when  the  spontaneous  ignition  temperature 
is  reached.  Such  explosions  may  occur  even  if  the  amount  of 
accumulated  deposit  is  small. 

After-burning  of  deposit,  which  is  a  characteristic  feature  of 
most  " explosions"  in  large  moderate  pressure  compressors,  does 
not  occur  in  high  pressure  compressors.  If  an  explosion  occurs 
in  the  very  confined  spaces,  it  is  very  violent  and  usually  shatters 
the  piping,  receiver,  etc. 

Note:  Valve  pockets  or  discharge  chambers  and  pipes  should  be  so 
designed  that  there  are  no  cavities  where  mixtures  of  oil  vapor  and  air 
may  remain  stagnant. 

Spontaneous  Ignition  Temperatures. — The  temperature  at 
which  oil  vapor  and  air  ignite  spontaneously,  i.e.,  without  the 
aid  of  a  spark,  is  higher,  the  lower  the  viscosity  of  the  oil.  Speaking 
generally,  the  more  complex  and  the  more  viscous  a  petroleum 
product  is,  the  lower  is  its  spontaneous  ignition  temperature. 
For  example,  kerosene  ignites  spontaneously  in  air  at  a  lower 
temperature  than  petrol.  The  compression  in  kerosene  oil 
engines  is  lower  than  in  petrol  engines  for  this  very  reason,  as  the 
danger  of  preignition  is  greater  with  kerosene. 


414  PRACTICE  OF  LUBRICATION 

It  will,  therefore,  be  realized  that  the  danger  of  explosions  is 
not  lessened  by  the  use  of  very  high  flash  point  oils.  Quite  apart 
from  the  fact  that  such  oils  are  very  viscous  and  favor  formation 
of  deposits,  the  mixture  of  air  and  vaporized  oil  is  spontaneously 
ignited  at  lower  temperatures  than  with  a  lower  viscosity  oil. 
It  might  be  asked,  why  then  not  go  to  the  other  extreme  and  use 
very  low  flash  oils?  Up  to  a  certain  point  this  view  is  certainly 
justified  and  correct.  But  with  very  volatile  oils,  although  they 
will  tend  to  keep  the  internal  conditions  clean,  and  thus  minimize 
danger  of  explosion,  yet  they  vaporize  so  much  exposed  to  normal 
compressor  temperatures,  that  the  presence  of  vapors  in  the 
compressed  air  will  become  troublesome,  and  furthermore  such 
oils  will  not  satisfy  the  requirements  as  regards  lubrication. 
Too  thin  oils  will  not  seal  the  pistons  and  will  cause  excessive 
internal  friction  and  wear. 

In  view  of  what  is  said  above  its  seems  probable  that  very  few 
explosions  have  been  caused  on  the  discharge  side  of  a  compressor 
by  injecting  kerosene  into  the  compressor  for  cleaning  purposes; 
but  when  kerosene  explosions  have  occurred  they  have  usually 
been  in  the  compressor  cylinder  itself,  the  ignition  taking  place 
through  the  suction  valves  on  the  approach  of  a  naked  light. 
For  the  same  reason,  no  naked  light  should  be  used  when  opening 
up  receivers  or  inter-coolers  for  examination. 

The  following  case  shows,  however,  that  the  flame  caused  by 
the  presence  of  kerosene  may  be  carried  right  through  the 
compressor  and  ignite  a  mixture  of  air  and  oil  vapor  on  the 
discharge  side. 

"In  a  compressor,  in  which  the  valves  had  been  reseated  and  the 
cylinder  cleaned  out,  the  cleaning  was  done  with  kerosene.  When  the 
compressor  was  started  up,  the  engine  attendant  came  to  the  conclusion 
that  something  was  wrong  with  one  of  the  suction  valves,  and  took  up 
a  candle  for  the  purpose  of  inspecting  it.  The  result  was  an  explosion, 
the  discharge  pipe  being  blown  to  pieces  for  a  length  of  about  ten  yards. 
It  was  evident  that  a  quantity  of  kerosene  was  pocketed  in  the  suction 
valve  chamber,  and  that  as  the  engine  acquired  the  usual  working  tem- 
perature, after  a  short  run,  the  heat  was  sufficient  to  vaporize  the  kero- 
sene. When  the  engine  attendant  inspected  the  valve,  the  cand'e 
flame  ignited  the  kerosene,  the  flame  was  carried  through  to  the  dis- 
charge pipe  and  the  explosion  followed." 

Air  Compressor  Rules. — The  following  rules  should  be  observed 
in  order  to  avoid  danger  of  explosions. 

(1^  Intake  air  should  be  taken  from  outside  the  engine  room, 
should  be  cold,  clean,  and,  if  necessary,  filtered. 

(2)  Sparing  and  uniform  amount  of  a  carefully  selected  com- 


BLOWING  ENGINES- AND  AIR  COMPRESSORS  415 

pressor  oil,  should  be  supplied,  with  frequent  drainage  of  inter- 
cooler  and  after-cooler  for  water  and  oil. 

(3)  Good  cooling  of  cylinder  should  be  practised,  including 
discharge  valve  chambers,  as  abnormal  temperatures  emanate 
from  these  valves.     The  cooling  water  must  always  be  turned  on 
before  the  air  compressor  is  started. 

(4)  Temperatures  should  be  taken  regularly  of  intake  and 
discharge  air,  as  abnormal  rise  in  temperature  is  a  sure  indication 
of  trouble. 

(5)  An  after-cooler  should  be  fitted  in  discharge  line  before 
the  receiver  under  difficult  conditions,  so  that  only  cold  air  enters 
the  receiver. 

(6)  Compressor  pressure  gauges  should  be  periodically   ex- 
amined and  corrected  by  comparison  with  standard  gauges. 

(7)  There  should  be  frequent  inspection  and  cleaning  of  water 
jackets,   valves,   discharge   pipe,   after-cooler  and  receiver;  in 
multiple  stage  air  compressors,  discharge  valves  should  be  ex- 
amined every  week;  low  pressure  valves  every  month;  receiver 
and  coolers  every  month  to  every  six  months,  depending  upon 
the  conditions. 

(8)  Kerosene  should  never  be  used  for  cleaning  the  compressor 
or  pipes  internally,   as  it  evaporates  and  forms  an  explosive 
mixture  with  the  air.     Soap  and  water  should  preferably  be  used 
for  cleaning,  the  surfaces  being  afterwards  wiped  clean  and  oiled 
with  compressor  oil  to  prevent  rusting  while  standing. 

SELECTION  OF  OIL 

Air  compressor  oils,  in  view  of  what  is  said  in  the  preceding 
chapter,  should  preferably  be  pale  colored  straight-run  distil- 
lates, highly  refined  and  filtered,  containing  as  few  unsaturated 
hydrocarbons  as  possible.  Air  compressor  oils  should  preferably 
contain  little  or  no  cylinder  stock. 

Where,  in  order  to  obtain  a  heavy  viscosity,  the  admixture  of 
filtered  cylinder  stock  becomes  necessary,  the  distilled  oil  should 
be  as  viscous  as  possible  so  as  to  minimize  the  percentage  of 
cylinder  stock  required  in  the  finished  oil. 

Air  compressor  oils  of  four  different  viscosities  are  required  to 
lubricate  the  cylinders  and  valves  o"  all  types  of  blowing  engines 
and  air  compressors,  as  indicated  in  table  No.  21. 

These  four  oils  are  usually  straight  mineral  oils  but  for  multiple 
stage  compressors,  as  Diesel  compressors,  oils  Nos.  2  and  3  are 
recommended  and  should  preferably  contain  from  3  per  cent,  to 
6  per  cent,  of  a  non-drying,  acid  free,  fixed  oil. 


416 


PRACTICE  OF  LUBRICATION 
TABLE" No.  21 


Compressor  oil 

Saybolt 

viscosity 

Flashpoint           Flashpoint 
open,  °F.            closed,  °F. 

104°F. 

212°F. 

No.  1 

150" 

36" 

380 

355 

No.  2 

350" 

53" 

400                375 

No.  3 

650" 

70"                425 

400 

No.  4l 

1500" 

120"                510 

475 

1  Compressor  Oil  No.  4  is  a  filtered  steam  cylinder  oil. 

The  following  chart  gives  specific  recommendations  for  the 
various  types  of  blowing  engines  and  air  compressors. 

LUBRICATION  CHART  No.  12  FOR  BLOWING 

ENGINES  AND  AIR  COMPRESSORS 


No.  of  stages 

Final  air 
pressure,  Ibs. 
pr.  sq.  inch 

Compressor  oil 

•'; 

. 

Blowing  engines: 

Blowing  cylinder  horizontal,  no  tail 

rod                 

Single  stage 

10-30 

Compressor  Oil  No.  3 

Blowing    cylinder   horizontal,    with 

tail  rod                           

Single  stage 

10-30 

Compressor  Oil  No.  2 

Blowing  cylinder  vertical  

Single  stage 

10-30 

Compressor  Oil  No.  1 

or  No.  2. 

Air  Compressors: 

Small  compressors 

Compressing  less  than  1000  cu.  ft. 

of  free  air  per  minute. 

Small  compressors  are  usually  en- 

Single stage 

Below  70 

Compressor  Oil  No.  1 

closed  and  use  the  same  oil  for 

Two  stage 

Below  150 

Compressor  Oil  No.  1 

cylinders  and  bearings 

Single  stage 

70-120 

Compressor  Oil  No.  2 

Two  stage 

150-450 

Compressor  Oil  No.  2 

Large  Compressors 

Compressing  more  than  1000  cu. 

ft.  of  free  air  per  minute. 

Horizontal  cylinders,  no  tail  rod 

(  Single  stage 
I  Two  stage 

Below  70     1 
Below  150  / 

Compressor  Oil  No.  3 
or  4. 

Horizontal  cylinders,  with  tail  rod 

{Single  stage 
Two  stage 

Below  70     1 
Below  150  / 

Compressor  Oil  No.  2 
or  3. 

For  large  compressors  compressing 

Compressor  Oil  No.  3 

above  the  pressures  given 

or  4. 

Large  hcrizontal  compressors  are  usu- 

ally open   type  and  use  separate 

bearing  oils  externally. 

Large    vertical   compressors   are   fre- 

quently   enclosed    type,    employ- 

ing force  feed  circulation  for  the 

bearings  and  the  same  oil  is  used 

throughout. 

NOTE  1. — Where  a  compressor  is  delivering  air  to  air- worked  engines 
placed  in  confined  spaces  '(tunnel  work,  etc.)  use  a  heavier  viscosity  (less 
volatile)  oil  than  the  one  indicated  in  the  chart. 


BLOWING  ENGINES  AND  AIR  COMPRESSORS  417 

DRY  AIR  PUMPS 

Dry  air  pumps  or  vacuum  pumps,  as  for  example  employed  in 
condenser  plants  for  steam  engines  or  steam  turbines,  are  a  kind 
of  air  compressors;  they  compress  the  small  amount  of  air  leaking 
into  the  system  and  discharge  it  at  atmospheric  pressure. 

Dry  air  pumps  are  often  constructed  with  slide  valves,  and  the 
lubrication  of  these  valves  is  troublesome  and  difficult.  The  oil 
is  subjected  to  the  vacuum  under  conditions  of  high  temperature, 
due  to  the  surfaces  being  in  touch  with  hot  steam  and  to  the 
additional  heat  created  by  valve  friction.  The  result  is  that  the 
oil  is  distilled,  ''vacuum-distilled,"  and  is  oxidized  by  the  air, 
forming  a  sticky  carbonaceous  deposit.  The  remedy  lies  in 
using  the  oil  with  the  utmost  economy  and  applying  it  regularly 
and  uniformly,  preferably  by  means  of  mechanically  operated 
lubricator.  The  less  oil  consumed,  the  less  carbon  is  formed.  An 
excellent  idea  is  to  introduce  a  jet  of  steam  through  a  ^-inch 
exhaust  steam  pipe  taken  from  the  steam  engine  driving  the  air 
pumps  (as  for  example  in  the  Alberger  pump).  There  must  be 
no  valves  in  this  pipe;  this  admission  of  moist  steam  greatly 
minimizes  the  formation  of  carbon. 

Many  engineers,  when  they  have  experienced  trouble  with  a 
medium  viscosity  compressor  oil  jump  to  the  conclusion  that 
by  using  a  higher  flash  point  oil  the  carbonization  will  be  over- 
come; they  therefore  use  steam  cylinder  oils,  "the  thicker  the 
better/'  and  find  the  carbonization  much  worse  than  before, 
notwithstanding  their  endeavor  to  use  as  little  as  possible.  As 
the  oil  is  volatilized  during  use,  it  is  obvious  that  a  distilled  lubri- 
cating oil,  which  has  already  been  volatilized  when  it  was  being 
manufactured,  must  have  less  tendency  to  leave  a  residue  than 
steam  cylinder  oils  which  are  undistilled  oils. 

Experience  proves  that  the  best  results  are  obtained  by  using 
Compressor  Oil  No.  2,  as  pale  as  possible,  without  cylinder  stock 
and  preferably  slightly  compounded  so  as  to  make  it  combine 
with  the  moisture,  which  is  always  present. 


No.  4  Compressor  Oil  must  only  be  used  if  there  are  very  special  reasons 
for  using  such  a  heavy  viscosity  oil,  as  for  example  the  necessity  of  having; 
an  absolute  minimum  of  oil  vapor  in  the  compressed  air  or  bad  mechanical 
conditions  in  large  horizontal  compressors. 

NOTE  2. — Glycerine  must  be  used  for  compressors  in  breweries,  as  even 
slight  traces  of  mineral  oil  vapor  in  the  air  will  be  absorbed  by  the  beer  and 
affect  the  taste,  whereas  glycerine  has  no  detrimental  effect  whatever. 

NOTE  3. — For  three-  and  four-stage  compressors,  the  same  oils  are  recom- 
mended as  for  Diesel  Compressors  (see  page  528)  namely,  Compressor  Oils 
Nns.  2  and  3  compounded  with  3  per  cent,  to  6  per  cent,  of  fixed  oil. 

27 


418  PRACTICE  OF  LUBRICATION 

Similar  conditions  exist  in  a  number  of  other  vacuum  pumps, 
for  example,  the  pumps  used  in  connection  with  sugar  evaporat- 
ing pans. 

AIR  OPERATED  ENGINES  AND  PNEUMATIC  TOOLS 

Compressed  air  is  used  for  operating  a  variety  of  engines, 
machinery  and  tools  as  indicated  in  the  beginning  of  this  section, 
page  402. 

Air  Operated  Engines. — The  operating  temperatures  of  the 
engines,  etc.,  determine  what  viscosity  oil  is  to  be  used. 

Air  engines  operating  coal  cutters  are  usually  fairly  warm,  and 
demand  an  oil  like  Bearing  Oil  No.  5.  As  the  temperatures 
are  never  more  than  moderate,  there  is  no  danger  of  carboniza- 
tion taking  place,  so  that  a  bearing  oil  of  suitable  viscosity 
will  do  all  that  is  required.  As  a  rule,  the  operating  tem- 
peratures are  low,  particularly  when  the  engines  or  tools  oper- 
ate with  air  expansion,  because  the  air  becomes  cold  when  it 
expands. 

Such  low  temperatures  may  bring  about  trouble  by  the  lubri- 
cant congealing,  or  the  engine  becoming  choked  with  snow. 
The  amount  of  moisture  in  the  compressed  air  is  often  consider- 
able. When  for  example  warm  compressed  air  is  sent  down  the 
shaft  in  a  coal  mine  it  cools  and  some  of  the  moisture  condenses; 
if  it  is  not  efficiently  drained  out  just  before  reaching  the  engine, 
it  will  freeze  into  snow,  lodge  in  the  exhaust  port,  and  accumu- 
late till  the  engine  pulls  up.  Even  if  the  lubricating  oil  does  not 
congeal,  it  will  not  clear  the  exhaust,  but  an  admixture  of  glycer- 
ine with  the  oil,  say  from  30  per  cent,  to  50  per  cent,  will  usually 
thaw  the  snow  and  keep  the  exhaust  clean.  The  mineral  oil 
should  have  a  cold  test  of,  say,  minus  25°F.  for  such  extreme 
cases,  but  usually  a  zero  cold  test  will  be  found  satisfactory. 
Large  air  operated  hammers  for  forging  purposes  should  prefer- 
ably have  the  oil  introduced  by  means  of  a  mechanical  lubricator, 
the  movement  being  taken  from  the  hand  lever  (see  Fig.  166). 
For  such  large  hammers  medium  bodied  oils  are  preferable,  as 
the  operating  temperatures  are  very  moderate. 

A  class  of  air  operated  engine  difficult  to  lubricate  is  the  air 
engine  in  torpedoes.  The  engine  may  have  three  cylinders 
enclosed  in  a  crank  case.  The  oil  is  forced  into  the  main  bearings, 
then  through  tiny  holes  in  the  crank-shaft,  say  J^oo  of  an  inch, 
into  the  crank  pins,  while  the  pistons  are  lubricated  by  splash 
from  the  crank  case.  The  oily  exhaust  air  from  the  engine  may 
be  used  for  lubricating  some  of  the  gears.  The  oil  is  forced  into 


BLOWING  ENGINES  AND  AIR  COMPRESSORS 


419 


the  bearings  by  means  of  air  pressure.  Towards  the  end  of  the 
run  the  air  pressure  drops  and  the  oil  supply  diminishes,  as  the 
resistance  towards  the  oil-flow  through  the  tiny  passages  remains 
unaltered.  Simultaneously,  the  air  is  heated  to  maintain  suffi- 
cient engine  power;  the  hot  air  burns  and  oxidizes  the  oil  in  the 
cylinders. 


FIG.   166. — Air  operated  hammer  with  mechanical  lubricator. 

The  conditions  are  therefore  irregular  oil  feed,  i.e.  overfeeding 
most  of  the  time,  and  exposure  to  higr/temperatures  and  air 
oxidation.  All  mineral  oils  produce  too  much  carbon  under 
these  conditions.  The  oil  which  hasjgiven  most  satisfaction  is 
cold-pressed,  highly  refined,  acid-free  neatsfoot  oil  or  its  equivalent. 


410 


PRACTICE  OF  LUBRICATION 


Such  an  oil  has  a  very  high  flash  point  without  being  unduly, 
viscous,  and  it  gives  practically  clean  lubrication. 

Pneumatic  Tools. — Pneumatic  tools  operate  at  very  high 
speed  (often  several  thousand  strokes  per  minute)  and  the  parts 
have  exceedingly  fine  clearances.  They  are  threrefore  very 
sensitive  and  the  air  consumption  may  easily  increase  25  per  cent, 
or  more  if  too  viscous  oils  are  used.  Oils  for  pneumatic  tools  should 
therefore  be  very  light  viscosity  oils  and  have  low,  sometimes 
very  low,  cold  tests  to  prevent  them  from  congealing  and  clog- 
ging the  tools.  The  oil  is  usually  fed  into  the  tool  at  intervals, 
say  every  hour.  If  a  tool  freezes  up,  an  injection  of  glycerine 
will  usually  thaw  the  snow  and  clear  the  exhaust,  after  which  the 
usual  low  viscosity  oil  may  again  be  applied. 


1  Oil  Chamber 

2  Filling  Plug 

2  3  Adjusting  Needle 

4  Dinction  of  Air 


FIG.  167. 


FIG.   168. 


Pneumatic  tool  oiler. 


Several  attempts  have  been  made  to  introduce  the  oil  sparingly 
and  uniformly  into  the  air  before  it  reaches  the  tool,  so  as  to  avoid 
under  lubrication.  Fig.  167  illustrates  an  oiler  with  a  needle 
adjustment  valve  used  by  the  Chicago  Pneumatic  Tool  Co.  Fig. 
168  shows  an  outside  view;  the  direction  of  the  air  must  be 
indicated. 

It  has  been  found  that  delays  caused  by  underlubrication  and 
stoppage  of  tools  are  reduced  as  well  as  the  cost  of  maintenance, 
when  such  oilers  are  used;  the  filling  of  the  oil  chambers  can  be 
done  in  the  toolroom  at  night,  when  the  tools  are  made  ready  for 
the  following  day's  service. 

Great  care  must  be  taken  to  ensure  that  the  air  supply  piping 
and  also  exhaust  piping  (if  the  latter  is  fitted),  shall  be  free  from 
dirt  and  chips,  and  that  they  be  thoroughly  blown  out  before 
final  connection  is  made  to  the  tool,  so  that  no  dust  or  foreign 
matter  will  be  carried  to  the  working  parts,  and  the  exhaust  pipe 


BLOWING  ENGINES  AND  AIR  COMPRESSORS  421 

will  be  clear.  There  is  usually  a  strainer  at  the  end  of  the  branch 
air  pipe  to  which  the  flexible  hose  is  attached.  This  strainer  is 
made  of  fine  mesh  brass  gauze  or  cloth  and  retains  scale  and 
impurities,  which  would  otherwise  injure  the  tools.  Even  a 
•small  piece  of  rubber  of  the  air  hose  will  put  the  tool  out  of  action. 

It  is  good  practice  to  immerse  pneumatic  tools  in  a  bath  of 
gasoline  or  kerosene  over  night,  then  blow  them  out  under  pres- 
sure and  oil  them  thoroughly  before  use. 

For  lubricating  the  gears  in  many  types  of  tools  a  filtered, 
poor  cold  test  (say  80°F.)  filtered  steam  cylinder  oil  will  give 
good  service;  it  will  be  semi-solid  at  ordinary  temperatures. 
This  oil  may  be  injected  into  the  gear  case  by  a  syringe,  say, 
every  few  working  hour-. 

It  is  important  that  the  compressed  air  pipe  system  be  properly 
drained,  to  prevent  water  getting  into  the  tools,  as  such  water 
would  cause  rusting  of  the  pipes  and  also  of  the  working  parts 
in  the  tools,  besides  clogging  the  tools  with  snow,  when  they 
operate  with  air  expansion. 

LUBRICATION  CHART  No.  13  FOR  AIR  OPERATED  ENGINES 

AND  PNEUMATIC  TOOLS 
Air  Operated  Engines: 

Air  Operated  Coal  Cutters  •    Bearing  Oil  No.  5     (see  page  128) 

This  oil  also  to  be  used  for  gen- 
eral lubrication  of  the  coal 
cutter. 

Air    Operated    Haulage    Engines         Refrigerator  Oil  No.  1  or  No.  2  or 
and  the  like.  mixtures  of  these  with  up  to  50 

per  cent,  of  glycerine  where  the  ex- 
haust is  liable  to  choke  with  snow. 
Large     Air     Operated     Forging         Bearing  Oil  No.  4. 

Hammers. 

Belt    Driven   Pneumatic   Forging         Air  Compressor  Oil  No.  2. 
Hammers  in  which  air  is  com- 
pressed  and   used   as   an   air 
buffer. 
Air  Engines  in  Torpedoes.  Highly  refined  neatsfoot  oil  with 

a  zero  °F.  cold  test. 
Pneumatic  Tools: 

Large  Pneumatic  Drills  and  the         Refrigerator  Oil  No.   1  or-    No.  2. 

like. 
Smaller  Pneumatic  Tools.  Light    pneumatic     tool     oil1     (see 

below). 

For    Gear    Cases   in    Pneumatic         Filtered  cylinder  oil  with  a    poor 
Tools.  cold  test,  say  80°F. 

1  Light  Pneumatic  Tool  Oil:  Pale,  straight-run  distillate,  highly  refined, 
having  a  Saybolt  viscosity  at  104°F.  of  approximately  80",  and  a  setting 
point  of  -25°F.  to  +15°F.  according  to  the  temperature  conditions  undor 
which  the  tools  operate. 


CHAPTER  XXVI 
REFRIGERATING  MACHINES 

Refrigerating  machines  are  used  for  producing  cold,  being  em- 
ployed in  a  great  variety  of  installations,  such  as  ice  manufac- 
turing plants,  breweries,  distilleries,  dairies,  sugar  factories, 
chocolate  factories,  slaughter  houses,  cold  storage  plants,  oil 
mills,  margarine  works,  stearine  works,  paraffin  works,  chemical 
works  of  various  kinds,  artificial  skating  rinks,  for  domestic 
purposes  in  large  houses  or  hotels,  hospitals,  etc.,  public  mortu- 
aries, mining  operations  (sinking  shafts  through  wet  sand),  also 
in  fishing  vessels  (freezing  fish),  food  transport  ships,  modern 
passenger  ships,  warships  (cooling  ammunition  chambers),  etc., 
etc. 

CLASSIFICATION 

There  is  a  great  variety  of  refrigerating  machines  in  use;  they 
can,  however,  be  classified  according  to  the  system  of  refrigeration 
employed,  as  follows : 

Absorption  Machines. 

Compression  Machines. 

Absorption  Machines. — These  machies  usually  operate  with 
ammonia.  They  are  manufactured  only  by  a  small  number  of 
firms.  No  lubrication  is  required  except  for  the  circulating 
pumps,  the  lubrication  of  which  presents  no  difficulty. 

Compression  Machines. — In  these  machines  the  cooling  me- 
dium, the  refrigerant,  at  one  stage  of  the  process  is  compressed  ; 
hence  the  name  compression  machines.  They  are  built  in  all 
sizes,  requiring  from  J^  horse  power  for  the  smallest  units  up 
to  600  horse  power  for  the  largest  units  in  large  installations. 

According  to  the  refrigerant  employed,  these  machines  may  be 
divided  into: 

Cold  Air  Machines 
Sulphurous  Acid  Machines 
Ammonia  Machines 
Carbonic  Acid  Machines 

the  refrigerants  being,  respectively : 

422 


REFRIGERATING  MACHINES  423 

Ail- 
Sulphur  Dioxide  (SO2) 
Ammonia  (NH3) 
Carbonic  Acid  ( CO2) 

Cold  air  machines  are  very  bulky  and  only  a  few  machines  are 
in  existence.  They  were  at  one  time  used  to  some  extent  on  board 
ship,  but  have  now  been  displaced  by  carbonic  acid  machines. 
They  usually  have  two  large  cylinders.  The  air  is  compressed 
in  one  of  these  cylinders  and  expands  and  cools  in  the  other  cylin- 
der. Glycerine  is  used  for  lubrication,  as  mineral  oil  gives  the 
air  a  burnt  odor,  which  taints  the  meat. 

Sulphurous  Acid  machines  are  bulky,  about  2j-£  times  the  size 
of  ammonia  machines  and  are  now  seldom  used.  As  the  sulj 
phurous  acid  is  a  lubricant  in  itself,  no  internal  lubrication  is 
required. 

Ammonia  machines  and  carbonic  acid  machines  are  practically 
the  only  two  types  of  refrigerating  machines  employed  in  modern 
installations. 

Ammonia  machines  are  generally  employed  in  land  installa- 
tions. They  take  less  power  to  operate  than  carbonic  acid 
machines,  and  the  pressures  carried  in  the  system  are  considerably 
lower  than  the  pressures  in  carbonic  acid  systems. 

The  principal  objections  to  ammonia  machines  are  that  ammo- 
nia leaking  out  from  the  system  has  an  unpleasant  penetrating 
odor  and  is  suffocating;  on  the  other  hand,  the  odor  makes  a 
leakage  easily  noticeable. 

Carbonic  acid  (C02)  machines  are  used  almost  exclusively 
on  board  ship;  they  take  up  considerably  less  room  than  ammo- 
nia machines.  Carbonic  acid  is  odorless;  a  leakage  is  therefore 
not  easily  detected  and  good  ventilating  arrangements  are 
essential. 

PRINCIPLE  OF  OPERATION 

Fig.  169  illustrates  the  main  elements  found  in  all  refrigerating 
plants  working  on  the  compression  system.  The  principle  of 
operation,  whether  ammonia  machines  or  carbonic  acid  machines 
are  employed,  is  exactly  the  same,  only  the  pressure  and  tempera- 
tures being  different. 

The  following  description  is  given  for  ammonia  machines,  the 
particulars  in  brackets  referring  to  carbonic  acid  machines. 

The  elements  are  the  following: 

Compressor. 
Oil  Separator. 


424 


PRACTICE  OF  LUBRICATION 


Condenser. 

Regulating  or  Expansion  Valve 

Evaporator. 

Dirt  Catcher. 

The  compressor  (1)  draws  in  gaseous  ammonia  from  the  suc- 
tion pipe  (7),  leading  into  the  suction  valve.  The  ammonia  is 
compressed  to  a  pressure  of  from  120  Ibs.  to  180  Ibs.  per  square 
inch  (CO2  from  900  Ibs.  to  1200  Ibs.  per  square  inch),  and  deliv- 
ered at  a  temperature  of  85°F.  to  150°F.  (C02  160°F.  to  170°F.) 
through  discharge  pipe  (8),  through  a  non-return  valve  (9)  into 
the  oil  separator  (2),  from  which  it  is  conveyed  through  pipe  (10) 
into  cooling  coils  in  the  condenser  (3). 


1  Compressor 

2  Oil  Seperator 

3  Condenser  3 

4  Expausiou  Yalve 

5  Evaporator 

6  Dirt  Catcher 

7  Suction    Pipe 

8  Discharge  Pipe 

9  Non  return  Valve 

10  Discharge   Pipe  to 
Condenser 

11  Brine  Tank 

12  Outgoing  Brine  Pipes 

13  Eeturu  Brine  Pipes 

14  Oil  Heater 


FIG.   169. — Refrigeration  system. 

Cold  water  passes  through  the  condenser,  cools  and  liquifies  the 
hot  ammonia.  The  cold  and  liquified  ammonia  now  passes 
through  the  regulating  or  expansion  valve  (4)  into  the  coils  of  the 
evaporator  (5). 

The  pressure  in  the  evaporator  coils  is  low,  from  15  Ibs.  to  45  Ibs. 
per  square  inch  (CO2  from  200  Ibs.  to  400  Ibs.  per  square  inch). 

The  effect  of  this  considerable  fall  in  pressure  is  that  the  li- 
quid ammonia  evaporates  and  in  doing  so  it  cools  down  consider- 
ably below  freezing  point,  the  temperature  being  from  minus  20°F. 
to  plus  15°F.  (C02:  minus  30°F.  to  plus  15°F.). 

The  cold  evaporator  coils  are  seldom  placed  directly  where  it  is 
desired  to  produce  cold.  Usually  they  are  placed  in  a  tank  (11), 
through  which  is  circulated  a  non-freezing  brine  (a  salt  solution) ; 
the  brine,  in  passing  over  and  around  the  cold  evaporator  coils, 


REFRIGERATING  MACHINES  425 

cools  in  contact  with  the  coils.  By  means  of  a  pump  the  cold 
brine  can  be  pumped  away  through  pipes  (12)  to  the  place  where 
it  is  desired  to  produce  cold.  The  brine  returns  through  pipes 
(13)  to  the  evaporator  tank  to  be  cooled  again. 

The  ammonia  vapor  leaves  the  evaporator  coils  at  a  tem- 
perature slightly  lower  than  the  temperature  of  the  brine,  and 
returns  through  the  dirt  catcher  (6)  to  the  compressor,  continu- 
ing the  cycle  of  operations  just  described. 

During  recent  years  a  new  system  of  ammonia  refrigeration, 
called  the  dry  compression  system,  has  come  into  use.  It  operates 
on  the  same  principle  as  those  machines  already  described,  which 
are  wet  compression  machines,  the  chief  difference  being  that 
the  temperature  of  the  ammonia  in  passing  through  the  com- 
pressor is  from  160°F.  to  190°F.  higher  than  the  temperature  in 
wet  compression  machines.  The  heat  developed  in  a  dry  com- 
pression machine  is  so  high  that  it  becomes  necessary  to  sur- 
round the  compressor  cylinder  with  a  cooling  water  jacket. 

CONSTRUCTION 

Small  compressors  are  driven  by  belt  or  rope  drive. 

Large  compressors  are  usually  operated  by  a  steam  engine,  the 
steam  engine  and  the  compressor  having  a  common  crank  shaft. 
Sometimes  the  steam  engine  cylinder  is  placed  in  tandem  with' the 
compressor  cylinder.  All  compressors  operate  at  low  speed,  as 
at  high  speed  the  operation  of  the  valves  becomes  irregular.  The 
compressors  are  built  either  vertical  or  horizontal,  the  practice  in 
this  respect  varying  in  different  countries. 

Most  large  compressors  and  many  small  compressors  are 
double-acting,  as  the  one  illustrated  in  Fig.  170,  but  frequently 
vertical  compressors  are  single-acting,  even  in  large  sizes,  there 
being  only  one  suction  valve  and  one  delivery  valve. 

The  cylinders  of  ammonia  compressors  are  constructed  chiefly 
of  cast-iron  or  steel,  as  copper  or  bronze  parts  would  be  attacked 
by  ammonia.  The  cylinders  of  carbonic  acid  machines  must  be 
made  very  strong,  on  account  of  the  high  working  pressure. 
The  cylinder  is  generally  made  of  a  forged  block  of  steel,  suitably 
bored  and  finished. 

Stuffing  Box/ — The  most  important  part  of  the  compressor  and 
the  most  difficult  part  to  keep  in  good  working  order  and  well 
lubricated,  is  the  stuffing  box.  The  object  of  the  stuffimg  box 
is  to  prevent  the  escape  of  ammonia  or  carbonic  acid  from  the 
cylinder,  and  also  to  prevent  air  or  moisture  from  the^  outside 
entering  the  compressor  through  the  stuffing  box. 


426 


PRACTICE  OF  LUBRICATION 


Fig,  170  illustrates  one  type  of  ammonia  compressor  stuffing 
box.  The  bottom  ring  consists  of  white  metal;  the  packing  rings 
are  of  cotton,  saturated  with  oil.  (1)  is  the  so-called  "lantern" 
which  has  a  hollow  space  filled  with  oil  around  the  piston  rod, 
then  follow  more  cotton  packing  rings,  and  sometimes  a  rubber 
ring,  all  the  packing  rings  being  squeezed  together  by  means  of  the 
stuffing  box  gland  (2).  For  sealing  this  gland,  oil  is  introduced 
through  the  inlet  (3),  and  overflows  through  the  outlet  (4).  Oil 
is  prevented  from  creeping  out  along  the  rod  by  means  of  the 
small  stuffing  box  (5). 

The  oil  film  on  the  piston  rod  absorbs  ammonia  vapors  from 
the  inside  of  the  compressor.  These  ammonia  vapors  escape 
in  the  lantern  and  rise  through  the  pipe  (6),  from  which  they 
are  passed  over  into  the  suction  pipe  of  the  compressor,  so  that 
no  refrigerant  is  lost. 


FIG.   J70. — Ammonia  compressor. 

As  the  oil  film  swells  on  the  piston  rod  inside  the  compressor, 
due  to  absorption  of  ammonia  or  CO2,  a  portion  of  oil  is  con- 
tinuously scraped  off  by  the  gland  on  the  outward  motion  of 
the  piston  rod  and  this  oil  serves  to  lubricate  the  piston. 

As  rubber  is  destroyed  by  the  action  of  mineral  oil,  and  swells 
when  absorbing  CO2,  most  manufacturers  have  discontinued  the 
use  of  rubber  in  gland  packings  in  favor  of  metallic  packing  or 
leather  packing. 

Fig.  171  shows  one  form  of  stuffing  box  for  a  CO2  machine. 
The  stuffing  box  is  very  accurately  machined  and  in  the  bottom 
is  introduced  a  bronze  ring,  after  which  three  sets  of  bronze  rings 
and  leather  rings  are  introduced,  then  the  lantern  to  which  the 
oil  is  applied  under  pressure,  subsequently  two  sets  of  bronze  rings 
and  leather  rings  followed  by  a  ring  of  cotton;  and  then  the 
stuffing  box  gland  keeps  the  whole  packing  in  position.  The 


REFRIGERATING  MACHINES 


427 


bronze  rings  are  all  a  good  fit  against  the  inside  of  the  stuffing 
box,  but  do  not  touch  the  piston  rod.  The  leather  packing  rings 
are  thinned  out  towards  the  cylinder  so  that  the^  form  an  elastic 
edge,  and  the  pressure  in  trying  to  escape  from  the  cylinder 
automatically  causes  the  leather  rings  to  press  against  the  piston 
rod  and  thus  to  prevent  leakage.  The  life  of  the  leather  packing 
is  usually  one  season,  sometimes  two. 

In  some  stuffing  boxes  there  is  an  oil  well  near  the  front  portion 
of  the  gland,  covered  with  a  lid.  The  gland  should  be  so  adjusted 
that  occasional  bubbles  of  CC>2  are  to  be  seen  rising  from  this 
well,  but  there  should  not  be  sufficient  CO2  escaping  to  cause 
foaming.  If  there  are  no  bubbles  the  packing  is  too  tight. 


FIG.  171. — Stuffing  box  with  leather  packing. 

Fig.  172  illustrates  a  metallic  packing  built  up  of  two  spirals 
screwed  into  one  another,  the  spiral  (1)  being  of  white  metal  and 
of  triangular  section;  this  gets  squeezed  tightly  against  the  rod 
when  the  stuffing-box  gland  (3)  is  tightened  up.  The  spiral  (2) 
is  also  of  triangular  section,  but  made  of  steel,  and  forces  itself 
towards  the  walls  of  the  stuffing  box,  leaving  spaces  near  the  rod 
where  the  lubricating  oil  can  accumulate  for  the  purpose  of 
lubricating  the  piston  rod.  The  small  stuffing  box  serves  the 
same  purpose  as  in  Fig.  170.  When  this  gland  is  in  good  condi- 
tion and  properly  adjusted,  only  very  little  oil  reaches  the  in- 
terior of  the  compressor. 

In  dry  compression  machines,  packings  containing  cotton,  leather 
or  rubber  cannot  be  employed,  as  they  will  be  destoyed  by  the 


428 


PRACTICE  OF  LUBRICATION 


heat.  Metallic  packings  are  used,  as  the  one  illustrated  in  Fig. 
172.  Another  type  of  metallic  packing  used  for  dry  compression 
machines  consists'of  a  number  of  rings,  each  in  two  halves  sur- 
rounding the  piston  rod  and  pressed  lightly  against  the  rod  by 
means  of  garter  springs.  The  rings  are  held  in  accurately  finished 
chambers,  forming  a  casing  around  the  piston  rod. 

When  packings  are  renewed  or  when  a  new  compressor  is 
started,  it  is  important  to  tighten  regularly  and  evenly  all  round, 
as  soft  packing  becomes  softer  through  use.  If  the  packings  are 
screwed  up  tight  at  once,  the  rod  will  probably  heat,  the  packing- 
may  be^destroyed  and  the  rod  get  scored. 


FIG.   172. — Stuffing  box  with  metallic  packing. 

Oil  Separator. — The  greater  portion  of  the  oil  reaching  the 
compressor  cylinder  passes  out  of  the  compressor  with  the  re- 
frigerant and  must  be  separated  out  by  means  of  an  oil  separator, 
for  reasons  given  later  on 

Fig.  173  illustrates  a  typical  oil  separator,  located  in  the  engine- 
room  near  the  compressor.  The  hot  gases  enter  through  the 
tube  (1)  and  leave  the  separation  chamber  (2)  through  the  pipe 
(3).  The  oil  is  separated  and  accumulates  in  the  bottom  of  the 
chamber  (2),  from  which,  by  opening  the  cocks  (4)  and  a  needle 
valve  (5),  it  is  allowed  to  pass  through  the  sight-feed  arrange- 
ment (6)  into  the  bottom  of  the  chamber  (7).  Below  this  cham- 
ber is  a  heating  chamber  (8)  through  which  hot  water  is  passed, 
entering  through  pipe  (9),  and  leaving  through  pipe  (10).  When 
the  oil  has  been  drained  into  the  chamber  (7),  the  needle  valve 
(5)  and  shut-off  cocks  (4)  are  closed;  the  hot-water  service  is  put 


REFRIGERATING  MACHINES 


429 


on;  the  heat  frees  the  oil  from  the  ammonia  vapors,  which  arc 
passed  out  through  the  pipe  (11),  leading  into  the  suction  pipe 
of  the  compressor.  Having  been  freed  from  ammonia  vapor, 
the  oil  is  blown  out  through  the  drawoff  cock  (12)  and  pipe  (13). 

In  some  oil  separators  a  mechanically  operated  rotating  plug 
is  continuously  transferring  the  separated  oil  from  the  separator 
(2)  into  the  chamber  (7). 

Great  care  'should  be  taken  in  filtering  and  purifying  oil  re- 
claimed from  the  oil  separator,  as,  if  it  is  not  entirely  freed  from 
impurities,  the  result  when  using 
the  oil  over  again  will  be  the  wear- 
ing of  the  piston  rod,  piston  and 
cylinder  walls. 

Expansion  Valve. — The  expansion 
valve  is  fitted  for  the  purpose  of 
wire-drawing  the  refrigerant  from 
the  high  pressure  existing  before  the 
valve  to  the  low  pressure  existing 
after  the  valve.  It  must  therefore 
be  capable  of  very  fine  adjustment. 

If  any  water  gets  mixed  with  the 
refrigerant,  this  water  usually  freezes 
in  the  expansion  valve  and  clogs  it; 
impurities  have  the  same  effect;  for 
this  reason  it  is  very  important  that 
the  expansion  valve  be  kept  abso- 
lutely clean. 

Dirt  Catcher. — In  the  suction  line 
of  the  compressor  is  fitted  a  short 
piece  of  pipe  provided  with  a  sieve, 
for  the  purpose  of  preventing  im- 
purities, such  as  iron  scale,  little 
pieces  of  packing  material,  or  even 

ice  (frozen  water)  from  entering  the  compressor.  This  sieve 
should  be  examined  every  day  or  so  in  the  case  of  a  new  com- 
pressor installation,  every  three  days  for  the  next  couple  of 
weeks,  and  later  on  once  every  two  months.  If  the  sieve  in 
the  dirt  catcher  is  allowed  to  get  full  of  impurities,  it  may  un- 
expectedly burst.  All  the  impurities  will  at  once  be  drawn  into 
the  compressor  and  almost  certainly  cause  serious  damage. 

METHODS  OF  LUBRICATION 

The  lubrication  of  the  compressor  piston  and  cylinder  is 
brought  about  entirely  by  the  oil  carried  through  to  the  interior 
ofjthe  cylinder  from  the  stuffing  box  by  the  piston  rod. 


10 


FIG.   173. — Combined  oil  separa- 
tor and  heater. 


430 


PRACTICE  OF  LUBRICATION 


There  are  three  principal  methods  of  lubrication,  viz : 

Bath  Oiling  System. 
Mechanically  Operated  Lubricator. 
Splash  Oiling  System. 

Bath  Oiling  System,  Fig.  174.  Oil  is  pumped  continuously  by 
means  of 'a  small  oil  pump  through  the  pipe  (1)  into  the  gland  (2) 
surrounding  the  piston  rod  (3);  the  oil  overflows  from  the  top 
through  pipe  (4)  back  again  into  the  oil  container,  re-entering 
the  oil  pump  and  circulating  afresh. 


FIG.   174. — Bath  oiling  system  for  stuffing  box. 

Figs.  175  and  176  show  a  bath  oiling  system,  where  the -oil  is 
not  circulated  but  seals  the  gland  by  maintaining  a  height  of  oil 
above  the  lantern  in  the  gland.  In  Fig.  176  the  oil  flows  to  the 
gland  under  the  full  compression  pressure. 

When  the  stuffing  box  gland  packing  is  too  loosely  adjusted,  an 
excess  amount  of  oil  will  find  its  way  into  the  compressor.  On 
the  other  hand,  if  the  packing  be  adjusted  too  tightly,  too  little 
oil  will  reach  the  interior;  the  piston  rod  will  heat  and  ma;y  even 


REFRIGERATING  MACHINES 


431 


become  scored  through  the  extreme  friction  and  pressure  exerted 
upon  the  rod  in  the  gland;  also  the  packing  will  suffer  from  the 
heat;  cotton  or  leather  becomes  brittle  and  small  portions  may  be 
carried  into  the  cylinder,  causing  excessive  wear. 

Mechanically  Operated  Lubricator. — In  dry  compression 
machines  experience  has  proved  the  necessity  of  employing 
mechanically  operated  force-feed  lubricators,  which  will  introduce 
a  small  quantity  of  oil  with  precision  and  regularity,  and  in 


FIG.  175. — Bath  oiling 
system  with  overhead 
tank. 


FIG.   176. — High  pressure  bath  oiling  system. 


which  the  oil  feed  can  be  adjusted  to  a  nicety.  The  mechanically 
operated  lubricator  is  driven  from  some  moving  part  of  the  engine, 
therefore  starts  and  stops  feeding  with  the  engine,  and  delivers 
the  required  quantity  of  oil  under  pressure  into  the  interior  of 
the  stuffing  box. 

Whereas  the  lubricating  oil  in  wet  compression  machines  readily 
adheres  to  the  moderately  warm  piston  rod,  and  thus  insures 
sufficient  oil  reaching  the  interior,  the  case  is  different  in  dry 
compression  machines.  Due  to  the  high  temperature  of  the 


432 


PRACTICE  OF  LUBRICATION 


piston  rod,  the  oil  film  will  be  thin  and  very  little  oil  will  reach 
the  interior  of  the  compressor,  unless  the  oil  be  introduced  into 
the  packing  under  pressure.  That  is  the  reason  why  mechanic- 
ally operated  force  feed  lubricators  are  used,  as  in  this  way 
the  oil  is  certain  to  be  carried  along  the  piston  rod  into  the  com- 
pressor, and  the  oil  feed  can  be  adjusted  to  the  correct  amount 
required  for  piston  lubrication. 


1  Hand  Pump 

2  Oil  Chamber 

3  Pipe  to  Gland 

2 


FIG.   177. — CO-i  pressure  lubricator. 

It  is  important  that  a  type  of  mechanically  operated  lubricator 
be  used  that  will  feed  oil  only.  Several  types  of  mechanically 
operated  lubricators  feed  air  with  the  oil;  the  air  thus  introduced 
into  the  stuffing  box  is  drawn  into  the  compressor,  increasing 
the  pressure  in  the  whole  plant,  and  considerably  decreasing 
the  efficiency. 

Fig.  177  illustrates  diagrammatically  a  lubricator  for  CO2 
machines  which  delivers  the  oil  into  the  gland  under  pressure, 
the  same  as  a  mechanically  operated  lubricator,  but  is  not  capable 
of  such  accurate  adjustment  or  control.  It  consists  of  a  cylinder 


REFRIGERATING  MACHINES  433 

in  which  there  is  a  piston  with  a  piston  rod.  The  one  side  of  the 
piston  is  subjected  to  the  condenser  pressure  of,  say,  70  atmos- 
pheres. The  other  side  (where  the  piston  rod  is)  holds  the  oil 
and  has  an  outlet  fitted  with  an  adjustable  throttle  valve,  through 
which  the  oil  passes  out  to  the  gland. 

The  difference  in  area  between  the  two  sides  of  the  piston  is 
about  10  per  cent,  and  causes  the  over-pressure  which  forces 
the  oil  into  the  gland.  By  this  method  leakage  of  CO2  from  the 
gland  is  entirely  obviated,  and  the  outer  gland  is  only  required 
to  prevent  leakage  of  lubricant. 

Splash  Oiling. — Some  few  makes  of  small  vertical  enclosed  type 
ammonia  and  C02  compressors  have  a  bath  of  oil  in  the  crank 
case,  into  which  the  crankpin  bearing  dips  and  splashes  the  oil 
to  all  parts. 

The  oil  level  should  be  a  little  below  the  underside  of  the 
crankshaft ;  if  it  is  too  high,  the  oil  will  froth  with  the  vapors  of 
the  refrigerant,  which  are  continuously  drawn  through  the 
crank  chamber. 

LUBRICATION 

The  objects  of  internal  lubrication  of  a  refrigerating  compressor 
are  firstly  to  lubricate;  secondly,  to  form  an  oil-sealing  film  so  as 
to  prevent  leakage  of  refrigerant  past  the  piston  and  out  through 
the  stuffing  box;  thirdly,  to  preserve  the  leather  or  rubber  which 
may  form  part  of  the  packing  material. 

If  too  little  oil  be  used,  the  oil  film  will  not  be  complete,  so  that 
excessive  friction  and  wear  takes  place  and  leakage  past  the 
piston  and  piston  rod  occurs.' 

If  too  much  oil  reaches  the  interior  of  the  compressor,  or  if  the 
separator  is  not  sufficiently  effective,  a  fair  amount  of  oil  will  be 
carried  over  into  the  condenser  and  through  the  expansion  valve 
into  the  evaporator  coils,  where,  owing  to  the  low  temperature, 
the  oil  becomes  sluggish  and  is  only  slowly  carried  through  the 
coils  back  again  to  the  compressor. 

The  oil,  in  passing  through  the  compressor,  is  exposed  to  the 
effect  of  the  ammonia  or  carbonic  acid,  under  moderately  high 
temperatures.  The  result  is  more  or  less  decomposition  in- 
dicated by  a  darkening  in  color  and  an  increase  in  gravity  and 
viscosity. 

Where  the  bath  oiling  system  is  employed,  the  system  must 
be  recharged  with  fresh  oil,  say  once  every  year. 

Oils  with  too  high  a  cold  test,  when  carried  over  into  the  separator 
coils  congeal  on  the  inside  of  the  tubes,  and,  as  oil  is  a  bad  heat 
conductor,  the  capacity  of  the  condenser  and  evaporator  will  be 

28 


434  PRACTICE  OF  LUBRICATION 

appreciably  reduced.  It  is  therefore  important  that  the  oil 
should  possess  a  sufficiently  low  cold  test,  so  as  not  to  become  too 
sluggish  to  flow  if  it  is  carried  over  into  the  evaporator  coils. 

The  oil  must  not  contain  any  moisture,  as  the  moisture  will 
freeze  and  cause  congealing  of  the  oil.  For  this  reason,  engine 
attendants  should  be  warned  not  to  put  the  oil' cans  near  suction 
pipes  covered  with  snow  in  the  vicinity  of  the  compressor,  as 
water  dropping  from  the  outside  of  such  pipes  may  drop  into 
the  oil  cans  and  contaminate  the  oil.  Care  should  also  be  taken 
that  the  "save-alls"  fitted  under  compressor  glands  and  else- 
where to  receive  the  waste  oil  are  so  made  that  no  water  dropping 
from  the  outside  of  the  suction  pipes  can  get  into  the  "save-alls" 
and  mix  with  the  oil.  Cases  have  been  known  where  so  much 
congealed  oil  has  accumulated  in  the  coils  of  the  evaporator 
that  they  have  become  almost  inoperative. 

The  oil  for  splash-oiled  vertical  compressors  must  have  a  very 
low  viscosity,  as  otherwise  it  froths  with  the  refrigerant;  the 
froth  fills  the  crank  chamber,  passes  the  piston,  and  clogs  the 
whole  system. 

Even  under  the  best  conditions  a  slight  amount  of  oil  will 
certainly  get  over  into  the  evaporator  coils  in  all  types  of  com- 
pressors, and  it  is  therefore  advisable  to  have  the  coils  thoroughly 
and  regularly  cleaned.  The  coils  are  best  cleaned  by  blowing 
through  dry  steam  and  afterwards  air  to  dry  the  pipes.  In  bad 
cases,  this  treatment  may  be  preceded  by  the  application  of  a 
solution  of  soda  ash. 

Glycerine  is  used  as  a  lubricant  where  the  packing  of  the 
piston  or  stuffing  box  consists  partly  of  rubber,  which  in  time 
is  destroyed  by  mineral  oil,  whereas  glycerine  has  no  appreciab  e 
deleterious  effect  on  rubber  or  leather.  With  a  packing  contain- 
ing only  leather  and  brass  or  white  metal,  such  as  Figs.  171  and 
172,  mineral  lubricating  oils  are  used,  and,  if  properly  selected 
and  of  good  quality,  will  be  found  superior  to  glycerine  in  reduc- 
ing the  piston  and  gland  friction. 

With  efficient  lubrication  the  piston  rod  assumes  a  smooth, 
glossy  surface,  covered  with  a  thin  clean  film  of  oil,  and  the 
piston  rod  maintains  a  moderate  temperature.  The  stuffing 
box,  as  well  as  the  piston,  will  be  perfectly  sealed,  so  that  no 
leakage  of  refrigerant  occurs. 

IRREGULARITIES 

Where  irregularities  occur  in  a  refrigerating  plant,  the  effect 
is  always  to  reduce  its  capacity  for  producing  cold.  The  cause 
of  the  irregularity  is  not  always  easy  to  trace. 


REFRIGERATING  MACHINES  435 

The  following  are  typical  causes  of  trouble: 

Broken  valve  springs,  preventing  the  valves  from  operating. 

Leaky  valves. 

Leaky  piston,  piston  rings  out  of  order. 

Dirty  condenser  coils :  deposit  from  dirty  cooling  water  on  the 
outside,  or  a  coating  of  oil  on  the  inside  of  the  tubes. 

Expansion  valve  clogged  or  frozen  (due  to  moisture  in  the  oil, 
the  use  of  poor  cold-test  oil,  or  impurities  from  the  pipes) . 

Inefficient  operation  of  the  evaporator  (due  to  oil  or  moisture 
congealing  on  the  inside  of  the  tubes,  or  to  salt  incrustations 
from  the  brine  on  the  outside  of  the  tubes).  <i 

Too  little  ammonia  or  carbonic  acid  in  the  system  (due  to  leak- 
age from  the  pipes  or  stuffing  box) . 

The  presence  of  air  in  the  system,  usually  indicated  by  too 
high  pressure  in  the  system  (air  admitted  through  stuffing  box). 

ICE  MAKING 

A  number  of  ice-making  plants  ashore  are  steam  driven.  The 
steam  after  passing  through  the  steam  engine  is  condensed  and 
subsequently  used  for  the  manufacture  of  can  ice.  Plate  ice  is 
not  made  from  condensed  steam. 

The  cylinder  oil  used  for  internal  lubrication  of  the  steam  en- 
gine may  find  its  way  into  the  ice,  which  is  most  objectionable, 
as  it  discolors  the  ice  and  gives  it  an  unpleasant  odor  and  taste. 

Troubles  with  discoloration  of  the  ice  can,  however,  be  traced 
to  a  variety  of  causes,  such  as  the  boiler  water,  the  raw  "make 
up"  water,  the  exhaust  steam  oil  separator,  and  the  water  filters. 

Water. — The  water  used  as  boiler  feed  water  for  the  boiler 
must  be  specially  selected;  it  must  not  be  hard;  it  must  be  free 
from  sodium,  calcium,  or  magnesium;  it  should  be  neither  acid 
nor  alkaline,  or  at  the  most  should  show  only  a  slight  reaction. 

The  boiler  should  be  of  ample  capacity  for  developing  the 
amount  of  steam  required;  the  water  level  in  the  boiler  should 
never  be  allowed  to  rise  too  high  and  should  be  as  constant  as 
possible;  otherwise,  priming  of  the  boiler  occurs  and  salts  in  solu- 
tion and  impurities  will  be  carried  over  with  the  steam  into  the 
steam  engine  and  finally  mix  with  the  water  used  for  ice  making. 

Unsuitable  water,  used  in  the  boiler  or  as  raw  "make  up" 
water,  produces  discolored  ice. 

Oil  Separator. — It  is  the  duty  of  the  oil  separator  to  remove  as 
much  as  possible  of  the  oil  contained  in  the  exhaust  steam.  The 
oil  and  moisture  from  the  steam  separate  out  in  the  bottom  of  the 
separator  and  are  removed  at  regular  and  frequent  intervals, 


436  PRACTICE  OF  LUBRICATION 

automatical!}  or  non-autornatically.  Most  of  the  oil  not  caught 
by  the  oil  separator  will  separate  out  in  the  re-boiler  (in  which  the 
water  is  heated  and  freed  from  air  bubbles)  and  is  automatically 
skimmed  off  the  surface.  Any  traces  of  oil  still  left  should  be 
caught  in  the  water  filters  (coke,  charcoal,  or  gravel). 

Filters. — Rust  from  the  pipes  and  impurities  of  various  kinds 
gradually  accumulate  in  the  niters.  It  is  therefore  necessary  to 
clean  or  renew  the  filtering  material  at  least  once  every  season. 

Steam  Cylinder  Oil. — When  using  compounded  steam  cylinder 
oils,  particularly  dark  cylinder  oils,  some  of  the  oil  may  pass 
not  only  the  oil  separator,  but  also  the  re-boiler  and  even  the 
filters,  finally  appearing  in  the  ice. 

Filtered  cylinder  oils  separate  easily  from  the  water.  A  good 
grade  of  filtered  cylinder  oil  is  therefore  to  be  recommended  for 
steam  engines  in  ice-making  plants;  and  if  a  good  type  of  me- 
chanically operated  lubricator  is  employed,  so  that  the  oil  can 
be  introduced  in  the  best  manner  and  used  economically,  the  use 
of  a  compounded  filtered  cylinder  oil  in  place  of  a  straight  mineral 
oil  is  permissible,  containing  not  more  than  3  per  cent,  acidless  tal- 
low oil,  as  the  admixture  of  tallow  oil  will  enable  the  cylinder 
oil  to  be  used  exceedingly  economically,  and  better  lubrication 
will  be  obtained. 

The  little  oil  which  will  be  present  in  the  exhaust  steam  is 
easily  taken  care  of  by  the  oil  separator,  or,  at  any  rate,  by  the 
re-boiler  or  filters. 

LUBRICATION  CHART  FOR  REFRIGERATING  MACHINES 

Refrigerator  oils  must  be  straight  mineral  oils.  Compounded 
oils  have  too  high  a  setting  point,  they  combine  to  some  extent 
with  ammonia,  more  or  less  saponification  taking  place,  and  they 
are  rather  inclined  to  absorb  moisture  from  the  atmosphere, 
which  is  very  undesirable.  Only  low  viscosity  is  required,  the 
setting  point  being  of  supreme  importance. 

For  most  refrigerators  in  ice-making  plants  an  oil  with  a  zero 
cold  test  will  be  satisfactory,  but  many  CO2  machines  operate 
with  lower  evaporator  temperatures  than  is  the  case  in  ice 
making  plants.  A  cold  test  of  —  25°F.  will  however  satisfy  the 
vast  bulk  of  refrigerating  compressors.  Many  ice  making  plants 
prefer  to  use  an  oil  with  a  better  cold  test  than  zero  F.  in  order 
to  have  an  extra  margin  of  safety  against  the  oil  congealing  in 
the  system. 

Oils  specially  low  in  viscosity  are  required  for  small  splash  oiled 
vertical  compressors  to  avoid  frothing. 


REFRIGERATING  MACHINES  437 

To  withstand  the  heat  in  the  compressor  without  serious  de- 
composition, refrigerator  oils  should  be  highly  refined  and  highly 
filtered,  pale  colored,  straight-run  distillates,  containing  as  few 
unsaturated  hydrocarbons  as  possible. 

Experience  proves  that  three  mineral  refrigerator  oils  having 
the  viscosities,  setting  points  and  open  flash  points  shown  in 
Table  No.  22  will  satisfy  all  requirements. 

TABLE  No.  22 


Refrigerator  oil 

Suybolt  viscosity 
at  104°F., 
in  sees. 

Setting  point,            Flash  point  open, 
°F.                                 °F. 

No.  1 

130-180 

0 

340-380 

No.  2 

130-180  . 

-25 

320-360 

No.  3 

60-  70 

Below  -  40 

Above  300 

These  three  mineral  oils  and  glycerine  are  recommended  for 
the  following  types  of  compressors: 

LUBRICATION  CHART  No.  14 
FOR  REFRIGERATING  COMPRESSORS 

For  compressor  For  bearings 


Cold  air  machines Glycerine  Bearing  Oil  No. 

1    4 
Ammonia  machines,1  open  type Refrigerator  Oil  |  Bearing  Oil  No. 

No.  1  or  2.         !    3  or  4. 
Carbonic  acid  machines,1  open  type  !  Refrigerator   Oil!  Bearing  Oil  No. 

No.  2.  !    3  or  4. 

Small   vertical    enclosed   type   splash-  Refrigerator   Oil;  Refrigerator   Oil 


oiled  machines,  whether  ammonia  or     No.  3. 


No.  3. 


carbonic  acid. 

Large  vertical  enclosed  type,   splash-i  Refrigerator   Oil  Refrigerator   Oil 
oiled  machines,  whether  ammonia  or     No.  2.  No.  2. 

carbonic  acid. 


1  When  rubber  forms  part  of  the  packing  in  the  stuffing  box  gland,  glycer- 
ine must  be  used  and  not  mineral  refrigerator  oil. 


CHAPTER  XXVII 
GAS  ENGINES 

In  order  that  the  reader  may  understand  and  appreciate  the 
lubricating  problems  met  with  in  connection  with  gas  engines, 
it  becomes  necessary  to  give  first  of  all  a  picture  of  the  mechanical 
and  operating  conditions. 

The  subject  has  been  divided  into  "Small  and  Medium  Size 
Horizontal  Gas  Engines,"  "Large  Horizontal  Gas  Engines" 
and  "Vertical  Gas  Engines."  For  each  group  of  engines  are 
given  particulars  of  typical  engines  and  the  methods  of  lubrica- 
tion. Some  information  follows  in  regard  to  cooling  and  gas, 
both  of  which  have  an  important  bearing  upon  the  lubrication 
of  gas  engines.  The  formation  of  carbon  deposits  is  then  treated 
in  detail,  and  finally  the  important  part  played  by  the  oil  itself, 
and  the  correct  grades  to  be  recommended  for  the  principal  types 
of  engines. 

SMALL  AND  MEDIUM  SIZE  HORIZONTAL  GAS  ENGINES 

Classification. — Small  horizontal  gas  engines  have  only  one 
cylinder;  they  develop  from  1  to  50  H.P.  and  operate  at  high 
speeds,  ranging  from  500  to  190  R.P.M.  Medium  size  horizontal 
gas  engines  are  made  with  one  or  two  cylinders;  the  power  de- 
veloped per  cylinder  ranges  from  50  to  250  H.P.  and  the  speeds 
range  from  190  to  130  R.P.M. 

The  cylinders  are  always  water  cooled  and  where  the  power 
per  cylinder  exceeds  150  H.P.  the  piston  must  also  be  water  cooled. 
Indeed,  many  builders  employ  water  cooled  pistons  in  engines 
ranging  in  sizes  from  80  H.P.  per  cylinder  upwards. 

Small  and  medium  size  engines  are  practically  always  of  the 
four-stroke  cycle  type,  and  in  view  of  the  foregoing  ma>  be  classi- 
fied as  shown  in  Table  No.  23: 

TABLE  No.  23 


No.  of  cylinders 


Revolu- 
tion.per 


Small  size One  cylinder.  1-50       500-190 

Medium  size  (without  water-  Usually  one;  sometimes     50-150    190-140 
cooled  pistons)  ;    two,  three  or  four. 


Medium    size    (with    water-  Usually  one;  sometimes 

cooled  pistons)  two,  three  or  four. 

I . 

438 


80-250    180-130 


GAS  ENGINES 


439 


The  cylinders  of  medium  size  engines  may  be  arranged  in 
various  ways  (Fig.  178) : 

Two  cylinders,  opposed — The  Opposed  Type  Engine  (Fig.  178A). 

Two  cylinders,  one  behind  the  other — The  Tandem  Engine 
(Fig.  1785). 

Two  cylinders,  side  by  side — The  Twin  Engine. 

Three  or  four  cylinders,  side  by  side — The  Multiple  Cylinder 
Engine  (Fig.  178C). 


11 


U    ,          niiiiiiiH 

J 

S 

FIG.   178. — Types  of  horizontal  gas  engines. 

METHODS  OF  LUBRICATION 

Principle  of  Operation. — The  four-stroke  cycle  principle  of  operation  may 
be  described  as  follows : 

First  or  Suction  Stroke. — Gas  and  air,  constituting  the  fuel  charge,  are 
sucked  into  the  cylinder  through  the  open  inlet  valve  as  the  piston  moves 
away  from  the  cylinder  head.  The  exhaust  valve  is  closed.  , 

Second  or  Compression  Stroke. — The  piston  moving  towards  the  cylinder 
head  compresses  the  fuel  charge.  Both  inlet  and  exhaust  valves  are  closed. 

Third  or  Power  Stroke. — Ignition  by  the  spark  of  the  compressed  fuel 
charge  produces  explosion  and  expansion  of  the  gases,  forcing  the  piston 
away  from  the  cylinder  head  during  the  power  stroke.  Both  inlet  and  exhaust 
valves  are  closed. 

Fourth  or  Exhaust  Stroke. — The  piston  moving  towards  the  cylinder  head 
drives  the  burned  gases  out  through  the  open  exhaust  valve.  The  inlet 
valve  is  closed. 

Thus  the  four  strokes  of  the  piston,  i.e.,  one  power  stroke  and  three  pre- 
paratory strokes,  complete  the  cycle  of  events;  hence  the  expression  four- 
stroke  cycle. 

Main  Bearings. — These  are  generally  ring-oiled  bearings, 
having  an  oil  reservoir  from  which  one  or  two  revolving  oil  rings 
continuously  carry  the  oil  to  the  bearing  surfaces.  In  some 
medium  size  gas  engine  the  main  bearings  are,  however,  fed  by 
gravity  from  an  elevated  tank  and  kept  in  continuous  circula- 
tion by  a  pump. 


440  PRACTICE  OF  LUBRICATION 

Crank  Pin  Bearing. — This  is  lubricated  by  means  of  the  well- 
known  banjo  arrangement.  The  oil  is  fed  into  the  banjo  either 
from  a  sight-feed  drop  oiler,  or  the  feed  may  come  from  a  me- 
chanically operated  lubricator. 

Piston. — Small  engines  are  often  fitted  with  only  one  oiler  to 
supply  the  piston  and  wrist  pin.  The  surplus  oil  on  the  piston 
collects  in  a  groove  at  the  top  and  through  a  tube  drops  into  the 
wrist  pin  bearing,  more  or  less  contaminated  with  carbon.  With 
this  method  it  is  always  necessary  to  overfeed  the  piston  in  order 
to  ensure  a  reasonable  supply  of  oil  reaching  the  wrist  pin.  Many 
small  engines  and  most  medium  size  engines  have  therefore 
separate  oilers  for  piston  and  the  wrist  pin,  so  that  the  right 
amount  of  oil  can  be  distributed. 

The  piston  oiler,  if  it  be  a  sight  feed  drop  oiler,  should  pref- 
erably be  provided  with  a  ball  check  valve  to  prevent  "blow 
back"  of  escaping  gases  into  the  sight  feed.  (See  Fig.  20, 
page  110.) 

Gravity  sight  feed  drop  oilers  will  vary  from  say  40  drops  per 
minute  when  nearly  full  to  16  drops  per  minute  when  nearly 
empty.  If  the  quantity  fed  at  a  lower  level  is  sufficient,  as  it 
must  be  if  the  engine  is  not  to  suffer,  the  extra  quantity  fed  when 
the  container  is  full  is  sheer  waste,  and  in  the  case  of  the  cylinder 
positively  detrimental.  The  oil  feed  is  very  susceptible  to  tem- 
perature changes  and  the  needle  valves  easily  choke  with  dirt. 
The  idea  has  therefore  been  steadily  gaining  ground  that  some- 
thing more  reliable  is  needed,  and  the  foremost  engine  builders 
are  adopting  a  centrally  placed  multi-feed  lubricator  operated 
mechanically  from  the  cam  shaft.  The  lubricator  should  be 
designed  on  principles  that  will  ensure  a  constant  uniform  oil 
feed,  independent  of  the  height  of  the  oil  level  in  the  container, 
and  independent  of  the  viscosity  of  the  oil.  Each  feed  should 
be  from  a  separate  pump  unit,  independent  of  the  other  feeds  and 
should  preferably  have  a  sight  fed  arrangement  showing  the  oil 
on  its  way  to  the  engine;  also  the  feeds  should  be  capable  of  being 
flushed  and  of  instantaneous  adjustment  between  wide  limits. 

The  lubricator  usually  has  an  operating  lever  actuated  by  a 
cam  on  the  cam  shaft;  the  oscillating  lever  gives  motion  to  the 
internal  mechanism  in  the  lubricator,  so  that  pump  plungers 
automatically  pump  oil  through  the  various  oil  pipes.  The 
individual  feeds  of  the  lubricator  once  adjusted  require  no  fur- 
ther attention. 

In  order  to  insure  that  the  oil  pipes  shall  be  always  full  they 
should  be  provided  at  the  extreme  ends  with  check  valves. 
When  the  lubricator  is  stopped  and  the  lubricator  ceases  to 


GAS  ENGINES 


441 


operate,  tlu;  check  valves  prevent  the  oil  from  running  out  of  the 
pipes.  The  pipes  are  thus  kept  constantly  full  of  oil  and  instant 
lubrication  is  assured  whenever  the  engine,  and,  consequently, 
the  lubricator  starts  to  operate. 


3  Oil  Injector 


FIG.   179. — Timed  oil  injection  to  piston  of  gas  engine  by  a  mechanical  lubricator 

Timed  Oil  Injection  to  the  Piston  (Fig.  179). — When  the 
mechanical  lubricator  is  designed  to  pump  oil  only  and  not  oil 
and  air,  the  piston  oil  feed  can  be  timed  to  inject  the  oil, under 
pressure  at  the  right  moment  V' 

and  to  the  ideal  place,  which  is 
between  the  first  and  second 
piston  ring,  when  the  piston  is  i  water  space 
at  its  most  outward  position.  2  Check  Valve 
This  enables  the  piston  to  carry 
the  oil  well  into  the  cylinder. 
Feeding  the  oil  in  this  way  the 
piston  will  act  as  an  oil  distrib- 
utor; cleaner  and  more  econo- 
mical lubrication  of  the  piston 
is  obtained  and  practically  no 
oil  runs  o  waste  from  the  lip  of 
the  liner.  It  is  necessary  that 
the  oil  should  be  fed  through  a 
combined  check  valve  and  oil 
injector  (see  Fig.  180)  the  end 
of  which  barely  touches  the 
piston,  so  that  for  every  im- 
pulse of  the  oil  pump  a  small 
portion  of  oil  is  wiped  off  by 
the  piston  and  taken  right  into  the  inner  portion  of  the  cylin- 
der, distributing  itself  uniformly  over  the  entire  surface.  Any 
deviation  from  this  practice,  either  by  feeding  the  oil  nearer 
thejront  of  the  liner  than  indicated,  or  feeding  it  through  a  lubri- 


FIG.   180. — Oil  injector. 


442  PRA.CTICE  OF  LUBRICATION 

oator  that  does  not  time  the  injection  of  the  oil,  will  mean  a  larger 
oil  consumption  (waste),  more  carbon  deposit,  and  a  lower  mar- 
gin of  safety. 

On  the  Continent  practically  all  gas  engines  are  fitted  with 
some  kind  of  mechanical  lubricator,  so  as  to  ensure  that  the  oil 
feed  to  the  piston  shall  be  as  regular  as  possible,  but  the  impor- 
tance of  timed  injection  does  not  appear  to  be  fully  realized. 
The  installation  of  such  a  mechanical  lubricator  means  extra  ini- 
tial cost  to  the  consumer  and  to  the  engine  builder,  but  it  also 
means  a  saving  in  oil  consumption  as  compared  with  sight  feed 
drop  oilers  of  as  much  as  50  per  cent.,  and  what  is  much  more  im- 
portant, it  means  a  greatly  increased  margin  of  safety,  as  well 
as  cleaner  and  more  efficient  lubrication  throughout. 

One  engine  builder  who  had  for  years  been  using  sight  feed 
drop  oilers  in  connection  with  pumps  (the  oil  dropping  from  the 
sight  feed  drop  oilers  into  the  oil  pumps)  found  that  after  install- 
ing mechanical  lubricators  of  a  good  make,  practically  all  their 
trouble  during  the  guaranteed  period  of  their  engines  ceased. 
In  many  cases  engine  attendants  forget  to  adjust  the  si£ht  feed 
drop  oilers,  forget  to  start  them  or  stop  them,  or  they  allow  them 
to  run  empty.  With  a  mechanically-operated  lubricator  there 
is  only  one  container  to  fill,  and  one  filling  of  the  container 
will  last  several  days;  less  attention,  is  therefore  required! 

Valve  Spindles  and  Cams. — The  valve  spindles  of  inlet  and 
exhaust  valves  (as  well  as  the  cams)  are  sparingly  hand-oiled 
but  in  the  case  of  larger  gas  engines,  say  above  50  H.P.,  it  is 
becoming  general  practice  to  lubricate  the  exhaust  valve  spindle 
by  one  of  the  feeds  from  the  mechanically  operated  lubricator. 
The  feed  must  be  very  sparing  and  absolutely  uniform.  With  an 
excessive  oil  feed  the  excess  oil  burns  and  carbonizes.  With 
too  sparing  a  supply  of  oil,  too  little  lubrication  is  provided. 
The  spindle  becomes  overheated  and  carbonizes  what  little  oil 
it  gets.  In  either  case  the  exhaust  valve  spindle  will  be  inclined 
to  " stick." 

LARGE  HORIZONTAL  GAS  ENGINES 

Large  gas  engines  are  used  for  driving  electric  generators  in 
iron  and  steel  works,  in  collieries,  occasionally  in  large  central 
power  stations,  and  ,  in  rare  instances,  in  textile  mills. 

Large  two-stroke  cycle  gas  engines  are  also  extensively  used 
in  iron  works  to  drive  blowing  engines  which  produce  compressed 
air  for  the  blast  furnaces. 

All  large  gas  engines  are  double  acting;  most  of  them  are  of 
the  four-stroke  cycle  type,  built  usually  as  tandem-cylinder 


GAS  ENGINES  .        443 

engines,  rarely  with  one  cylinder  only.  The  largest  power  units 
consist  of  two  tandem  engines  placed  side  by  side — a  twin  tandem 
engine — operating  an  electric  generator  mounted  between  them 
on  the  main  shaft.  Two-stroke  cycle  gas  engines  have  only  one 
cylinder  and  operate  at  a  lower  speed  than  four-stroke  cycle 
engines. 

TABLE  No.  24 

Classification  No.   of  cylinders, H. P.    per    cylinder!  11. P.M. 


15  ft* 


Four-stroke  cycle  double  acting. . . .    One  to  four         300  to  1500 
Two-stroke  cycle  double  acting One  400  to  2000 


METHODS  OF  LUBRICATION 

Internal  Lubrication. — The  cylinder,  stuffing  boxes,  and 
exhaust  valve  spindles  are  always  lubricated  by  means  of  a  me- 
chanically operated  lubricator  delivering  the  oil  under  pressure 
to  the  various  parts  and  operated  from  the  cam  shaft. 

Cylinder. — The  oil  is  introduced  into  the  cylinder  at  from  three 
to  six  points,  through  ^  inch  copper  pipes  from  the  mechanically 
operated  lubricator.  The  oil  inlets  are  sometimes  located  at  the 
middle  of  the  cylinder  of  four-stroke  cycle  engines,  but  in  the 
case  of  two-stroke  cycle  engines  this  is  not  possible  on  account 
of 'the  exhaust  belt  around  the  middle  of  the  cylinder.  In  this 
case  the  oil  inlets  are  placed  about  half-way  between  the  exhaust 
belt  and  the  cylinder  ends. 

It  is  important  that  the  oil  be  introduced  into  the  cylinder 
at  the  moment  when  it  will  be  fed  directly  to  the  piston  and  the 
piston  rings.  If  introduced  when  the  oil  inlets  are  uncovered, 
the  oil  is  burned  by  the  hot  gases,  resulting  in  waste  of  oil  and 
the  formation  of  deposits. 

Stuffing  Boxes. — The  stuffing  boxes  located  in  the  cylinder 
heads  are  the  parts  which  usually  give  the  most  trouble.  The 
oil  is  introduced  under  pressure  into  the  middle  of  the  stuffing 
box  and  distributed  over  the  entire  frictional  surfaces  of  the 
packing  rings.  (See  Fig.  181.)  The  packing  rings  are  usually 
cast-iron  rings  made  in  two  halves  and  held  together  around  the 
piston  rod  by  means  of  light  garter  springs.  Outside  the  pack- 
ing rings  there  is  occasionally  a  second  stuffing  box,  employing 
soft  packing. 

Exhaust  Valve  Spindles. — Although  the  exhaust  valve  guides 
surrounding  the  exhaust  valve  spindles  are  water  cooled,  it 
becomes  necessary  to  lubricate  the  spindles  with  a  uniform  and 


444 


PRACTICE  OF  LUBRICATION 


very  sparing  supply  of  oil  for  the  same  reasons  as  mentioned 
under  medium  size  gas  engines. 

Mixing  and  Inlet  Valves. — The  mixing  and  inlet  valve  spindles 
are  sparingly  hand  oiled,  except  in  very  large  engines,  where  they 
are  supplied  with  oil  through  separate  feeds  from  the  mechanic- 
ally operated  lubricator. 

Gas  and  Air  Pumps. — As  the  gas  and  air  are  sucked  into  these 
pumps  at  a  slight  vacuum  and  delivered  from  the  pumps  to  the 
working  cylinders  at  a  pressure  of  4  to  6  pounds,  the  tempera- 
ture of  the  pump  cylinder  walls,  due  to  compression,  is  not 
much  above  100°F.  There  is,  therefore,  no  need  for  water 
jacketing  these  cylinders  and  their  lubrication  presents  no  diffi- 
culties where  the  gas  and  air  are  clean. 


FIG.   181. — Stuffing  box  for  large  gas  engine. 

The  practice  has  been  to  feed  the  oil  through  sight  feed  drop 
oilers  into  the  centre  of  each  pump  cylinder,  with  additional 
oil  feeds  to  either  end  of  both  gas  and  air  valve  chambers.  Fre- 
quently, however,  an  accumulation  of  deposits  has  been  experi- 
enced due  to  moist,  dirty  gas,  and  overfeeding  of  the  oil,  the  im- 
purities adhering  to  the  excess  oil.  Under  these  conditions  it 
has  been  found  better  practice  not  to  lubricate  the  pump  cylinder 
and  valve  direct,  but  to  introduce  the  oil  uniformly  and  sparingly, 
by  means  of  a  mechanically  operated  lubricator,  through  atom- 
izers in  the  respective  intake  pipes. 

EXTERNAL  LUBRICATION 

Circulation  System. — In  the  external  lubrication  of  hirgc  gas 
engines  a  circulation  system  is  usually  employed.  The  lubrica- 


GAS  ENGINES 


445 


tion  of  main  bearings,  crank  pin,  cross  head,  tail-rod  support 
and  guides  is  accomplished  by  means  of  oil  fed  by  gravity  from  a 
top  supply  tank  through  a  distributing  pipe  and  its  branches, 
into  the  various  bearings.  Adjusting  valves  are  fitted  in  the 
branch  pipes  to  regulate  the  oil  feeds.  Having  done  its  work, 
the  oil  drains  back  to  the  bottom  receiving  tank. 

An  oil  pump  driven  by  the  engine  draws  the  oil  from  the  receiv- 
ing tank  and  delivers  it  through  an  oil  cooler  into  the  top  tank. 
If  more  oil  is  delivered  to  the  top  tank  than  is  required  for  the 
bearings,  the  surplus  oil  overflows  through  an  overflow  pipe  back 
into  the  receiving  tank.  The  top  tank  may  be  omitted  and  the 
oil  passed  directly  from  the  oil  cooler  into  the  distributing  pipe, 


FIG.   182. — Crosshead  of  large  gas  engine. 

in  which  case  it  becomes  necessary  to  have  a  relief  valve,  through 
which  the  surplus  oil  is  passed  back  into  the  bottom  tank. 

The  oil  is  delivered  to  the  crank  pin  through  the  hollow  crank 
shaft,  and  in  order  to  distribute  the  oil  well  there  are  usually 
three  or  four  radial  holes  (120°  apart)  through  which  the  oil 
reaches  the  large  bearing  surface. 

The  oil  for  the  crosshead  bearings  is  delivered  to  the  crosshead 
guide.  The  crosshead  shoe  is  so  long  that  the  oil  hole  in  the 
guide  is  never  uncovered;  consequently,  the  oil  is  enabled  to 
force  its  way  through  drilled  passages  in  the  crosshead,  as 
indicated  in  Fig  182. 


446  PRACTICE  OF  LUBRICATION 

To  give  an  idea  of  the  dimensions  of  bearings  and  oiling  system, 
the  following  two  examples  are  cited  as  typical  of  existing 
engines. 

Circulation  System  for   1000  B.H.P.     Two-stroke   Cycle  Single  Cylinder  Gas 

Engine 

Engine  speed 94  R.P.M. 

Quantity  of  oil  in  circulation 40  gals. 

Type  and  size  of  pump Plunger  pump,  \Y^"  dia.  X 

\Y^"  stroke. 

Speed  of  oil  pump 94  strokes  per  min. 

Height  of  oil  pump  above  oil  level  in  bot- 
tom tank 4  ft. 

Three  main  bearings 18"  diameter  X  33"  length. 

One  crank  pin , 18"  diameter  X  30"  length. 

Oil  delivery  pipe. 1^"  diameter. 

Oil  return  pipe 2"  diameter. 

All  waste  oil  flows  direct  to  bottom  oil  tank,  which  has  two 
vertical  strainers,  through  which  the  oil  passes  to  the  oil  pump; 
the  suction  pipe  is  fitted  with  a  strainer  and  a  non-return  valve 
(foot  valve). 

Circulation  System  for    1000   B.H.P.   Four-stroke    Cycle    Tandem    Cylinder 

Gas  Engine 

Engine  speed 140  R.P.M. 

Quantity  of  oil  in  circulation 80  gals. 

Type  of  oil  pump Rotary,  4"  wheels. 

Speed  of  oil  pump 140  R.P.M. 

Height  of  pump  above  oil  level  in  bot- 
tom tank .  . 6  ft. 

Three  main  bearings ;s.  .  .    16"  diameter  X  25.5"  length. 

One  crank  pin 15.5"  diameter  X  19.0"  length. 

Two  crosshead  bearings  for  forked  con- 
necting rod 9"  diameter  X  9.5"  length. 

Oil  delivery  pipe 2"  diameter. 

Oil  return  pipe 2"  diameter. 

All  waste  oil  is  led  to  a  separating  tank,  which  retains  most  of 
the  water  and  impurities.  The  oil  then  passes  through  a  filter 
before  being  delivered  to  the  bottom  oil  tank  through  a  strainer. 

Timing  Shafts  are  usually  supported  by  ring  oiled  bearings. 

Eccentrics  are  equipped  with  sight  feed  drop  oilers  or  auto- 
matic compression  grease  cups. 

Valve  Levers  are  sparingly  hand  oiled. 

Governor. — The  governor  is  oiled  partly  by  sight  feed  drop 
oilers  and  partly  by  hand. 


GAS  ENGINES 


447 


VERTICAL  GAS  ENGINES 

Vertical  gas  engines  are  principally  used  for  driving  electric 
generators  which  produce  current  for  lighting  or  for  operating 
electric  motors.  They  are  also  used,  occasionally,  for  driving 


TABLE  No.  25 


Type 


No.  of  cylinders 


H.P.  pei- 
cylinder 


R.P.M. 


four-  stroke  Cycle. 
Multiple  cylinder  tvpe  

One  to  six. 

5  to  125     35%25 

Multiple  tandem  cylinder  type  .... 

Four  to  twelve 

5  to  125     35?225 

Two-stroke  Cycle. 

Double  acting,  with  oil  or  water- 1  Two  to  four 
cooled  pistons. 


200  to  500 


air  compressors,  large  centrifugal  pumps,  refrigerating  plants, 
etc. 

Practically  all  vertical  gas  engines  are  of  the  four-stroke  cycle 
types. 

Some  large  two-stroke  c>cle  vertical  gas  en- 
gines have  been  developed  in  England,  but  may 
be  said  to  be  still  in  the  experimen  al  stage. 

Constructional  Points. — There  are  two  types  of 
vertical  four-stroke  cycle  gas  engines :  the  multiple 
cylinder  type  and  the  multiple  tandem-cylinder 
type  (shown  diagrammatically,  Fig.  183).  Mul- 
tiple cylinder  vertical  engines  are  rarely  built 
with  one  cylinder  only ;  they  generally  have  three 
or  four  cylinders.  The  multiple  tandem-cylinder 
type  usually  has  4  or  6  pairs  of  cylinders,  i.e.  8, 
or  12  cylinders,  and  is  developed  only  in  England: 
by  the  British  Westinghouse  Company  and  the 
National  Gas  Engine  Company. 

As  vertical  gas  engines  are  always  enclosed, 
and  the  cylinder  walls  copiously  supplied  with 
oil,  the  pistons  are  frequently  designed  with  oil 
scrapers  at  the  bottom  in  connection  with  grooves 
from  which  the  oil  can  be  drained  through  holes  pIG<  is  3.— 
to  the  interior  of  the  piston,  and  thence  down  Diagram  of  ver- 

...  .  .         tical    tandem- 

mto  the  crank  chamber.     Also  it  is  good  practice  type  gas  engine, 
to  design  the  pistons  in  two  parts,  inserting  be- 
tween the  top  and  bottom  portion  a  plate,  which  prevents  the 
oil  from  the  gudgeon  pin  splashing  into  the  hot  hollow  piston 
head,  where  it  would  otherwise  burn  and  char.     As  an  alter- 


448  PRACTICE  OF  LUBRICATION 

native  the  piston  may  be  cast  with  a  projecting  internal  lip 
above  the  gudgeon  pin,  the  hole  being  closed  by  a  plate. 

In  the  case  of  the  vertical  tandem-type  gas  engines,  the  two 
pistons  are  connected  by  means  of  a  piston  rod  working  in  a 
sleeve  between  the  two  cylinders.  The  air  below  the  top  piston 
is  compressed  on  the  downstroke  and  acts  like  an  air  buffer. 

Methods  of  Lubrication. — Vertical  four-stroke  cycle  gas  en- 
gines operate  at  high  speed.  In  order  to  prevent  the  lubricating 
oil  from  splashing  away  from  the  bearings,  all  external  motion 
parts  are  enclosed  in  a  crank  chamber  or  casing,  so  that  the  parts 
may  be  copiously  supplied  with  oil,  either  by  the  splash  system 
of  lubrication  or  by  the  force  feed  circulation  system. 

CRANK  CHAMBER  LUBRICATION 

Splash  Oiling  System  (Fig.  184). — The  lower  portion  of  the 
crank  chamber  is  filled  with  oil  to  the  level  indicated  in  the  draw- 
ing and  an  adjustable  overflow  pipe  is  fitted  to  one  end  of  the 
crank  chamber  in  order  to  maintain  a  correct  oil  level.  The 
bottom  ends  of  the  connecting  rods  dip  into  the  oil  and  splash  it 
to  all  parts  requiring  lubrication. 

Oil  is  fed  into  the  outer  main  bearings  by  sight  feed  drop  oilers. 
Leaving  these  bearings  the  oil  drops  into  the  crank  chamber  and 
thus  makes  up  for  the  amount  of  oil  that  goes  away  as  oil  spray 
or  is  burned  away  inside  the  cylinders.  In  place  of  sight  feed 
drop  oilers,  a  mechanically  operated  lubricator  is  preferably  em- 
ployed to  supply  oil  uniformly  to  the  main  bearings,  in  this  way 
making  the  lubrication  system  entirely  self-contained  and  auto- 
matic in  action. 

A  correct  constant  oil  level  must  be  maintained,  in  order  to 
secure  uniform  splash  to  all  parts  and  to  obtain  greatest  economy. 
Connecting  rods  should  dip  into  the  oil  to  the  same  depth,  and 
the  oil  level  should  be  lowered  until  the  formation  of  carbon 
deposits  on  the  pistons  is  reduced  to  a  minimum. 

Irregular  or  too  high  an  oil  level  means  waste  of  oil  and  excessive 
carbonization.  Too  low  an  oil  level  or  the  use  of  an  oil  too  heavy 
in  viscosity  means  unequal  distribution  and  insufficient  lubrication 
for  some  of  the  parts,  resulting  in  excessive  wear  of  those  parts. 
It  cannot  be  too  strongly  emphasized  that  an  adjustable  overflow 
should  be  installed,  in  order  that  the  correct  oil  level,  once 
established,  can  be  automatically  maintained. 

Force  Feed  Circulation  System. — This  system  delivers  the 
oil  under  a  pressure  of  from  5  to  20  pounds  per  square  inch  to 
all  bearings,  the  oil  leaving  the  gudgeon  pins  splashing  on  to  the 


GAS  ENGINES 


449 


cylinder  walls.     The  circulating  oil  sometimes  passes  a  filter  or  a 
cooler. 

Oxidation. — In  passing  through  the  main  bearings,  crank  pin 
bearings,  and  wrist  pin  bearings,  the  oil  is  subjected  to  high  tem- 
perature and  speed  of  the  rubbing  surfaces.  Oxidation  takes  place 


£-  s: 


U 

r      | 

i     i      i     i 

m 

i     i      i      i 

•  i 

FIG.   184. — Splash  oiled   vertical  gas  engine. 

which  is  indicated  by  a  darkening  in  color,  an  increase  in  vis- 
cosity and  gravity,  and  the  development  of  acidity. 

Temperature. — As  the  crank  chamber  is  enclosed,  the  heat 
radiated  from  the  pistons  and  cylinder  walls  is,  to  a  large  degree, 
retained  in  the  crank  chamber,  so  that  the  oil  in  the  crank  cham- 
ber gets  warm,  reaching  a  temperature  of  from  100°F.  to  160°F. 
If  a  temperature  of  140°F.  is  greatly  exceeded,  the  life  of  the  oil 
will  be  shortened,  and  it  may  throw  down  a  dark  deposit  caused 

29 


450  PRACTICE  OF  LUBRICATION 

by  oxidation  similar  In  thai,  which  may  lake  place  with  turbine 
oil. 

The  force  feed  circulation  system  is  always  employed  in  vertical 
four-stroke  cycle,  multiple  tandem-cylinder  gas  engin  s  and  is 
superior  to  the  splash  lubricating  system.  The  splash  system  is 
used  in  some  multiple  cylinder  engines,  but  the  majority  of  these 
engines  employ  the  force  feed  circulation  system. 

It  is  a  common  trouble  that  oil  in  the  crank  chamber  becomes 
contaminated  with  carbonized  matter  working  down  from  the 
pistons.  In  order  to  prevent  dirty  oil  from  the  trunk  pistons 
dropping  into  the  crank  chamber  some  builders  of  vertical  two- 
stroke  cycle  gas  engines  and  vertical  multiple  cylinder  four-stroke 
cycle  engines  raise  the  cylinders  above  the  crank  chamber  by 
means  of  a  distance  piece.  The  piston  rods  pass  through 
scraper  glands  and  are  connected  inside  the  crank  chamber  to 
crossheads. 

By  this  construction  carbonized  matter  can  be  prevented  from 
entering  the  crank  chamber,  but  as  the  pistons  are  not  lubricated 
by  splash  from  the  crank  chamber,  it  becomes  necessary  to  lubri- 
cate them  independently,  by  means  of  a  multiple  feed  mechanic- 
ally operated  lubricator.  This  practice  permits  the  use  of  a 
different  oil  for  piston  lubrication,  which  is  often  desirable. 

As  burned  gases  occasionally  escape  past  the  pistons  into  the 
crank  chamber,  this  is  provided  with  an  air-vent  pipe,  frequently 
fitted  with  a  fan,  which  sucks  away  from  the  enclosed  crank 
chamber  fumes  and  vaporized  oil.  At  the  same  time  cold  air  is 
constantly  drawn  through  the  engine  and  helps  to  cool  the  pistons 
and  crank  chamber. 

As  regards  the  piston  lubrication,  one  oil  feed  from  the  lubri- 
cator goes  to  each  piston,  delivering  the  oil  through  a  check  valve 
into  an  annular  oil  tube  surrounding  the  cylinder,  from  which  2, 
4  or  6  leads  go  through  the  water  jacket  and  distribute  the  oil 
over  the  piston  surface.  As  the  oil  is  introduced  at  one  point 
of  the  annular  oil  tube  it  is  likely  to  pass  into  the  cylinder  through 
the  leads  nearest  this  point,  so  that  the  opposite  side  of  the  cylin- 
der may  get  little  or  no  oil  direct  from  the  leads.  For  this  reason 
it  is  good  practice  to  have  each  point  of  entrance  to  the  cylinder 
fed  by  a  separate  oil  pump,  so  that  each  feed  can  be  controlled 
with  certainty.  Two  oil  feeds  suffice  up  to  21-inch  cylinders, 
one  feed  for  the  front  and  one  for  the  back  of  each  piston. 

Further,  the  oil  should  preferably  be  introduced  in  line  with  the 
level  between  the  first  and  second  piston  ring,  when  the  piston 
is  in  its  lowest  position.  The  oil  feeds  from  the  mechanically  op- 
erated lubricator  should  be  capable  of  independent  adjustment, 


GAS  ENGINES  451 

so  that  the  exact  amount  of  oil  required  can  be  supplied  to  the 
sleeves  and  pistons. 

Pistons. — The  piston  rings  should  be  in  good  condition  and 
pegged,  so  that  only  a  sufficient  amount  of  oil  for  full  lubrication 
will  reach  the  entire  piston  surfaces.  Too  much  oil  splashed 
from  the  crank  chamber  (too  high  oil  level,  too  high  oil  pressure), 
or  too  much  oil  fed  directly  to  the  piston,  means  that  excess  oil 
wi  1  pass  to  the  piston  tops,  where  it  will  burn  and  char  and  ulti- 
mately form  deposits. 

In  the  case  of  multiple  tandem  cylinder  engines,  care  should  be 
taken  that  the  quantity  of  oil  fed  from  the  mechanically  operated 
lubricator  to  the  top  pistons  and  the  sleeves  be  reduced  to  the 
exact  amount  required.  This  applies  also  to  multiple  cylinder 
engines  with  a  distance  piece  between  the  cylinders  and  the  crank 
chamber. 

The  importance  of  pegging  the  piston  rings  is  clearly  shown  by 
an  experience  related  in  "The  Gas  World"  for  May,  1918.  Hav- 
ing explained  that  preignition  occurred  badly  in  only  one  out  of 
several  4-cylinder  engines,  the  writer  continues : 

"I  believe  in  one  of  my  letters  I  mentioned  the  theory  I  had  previ- 
ously put  forward,  that  oil  vapor  passing*  the  pistons  might  account  for 
the  pre-ignition.  I  now  took  this  up  again  and  it  seemed  possible  that 
this  oil  vapor  might  result  from  the  high  oil  pressure  we  have  always 
carried  on  this  engine,  viz.  10  Ibs.  per  sq.  in.  A  reduced  pressure  was 
tried  and  a  better  run  was  obtained  before  pre-ignition  occurred  and  the 
pre-ignition  was  now  in  No.  2  cylinder,  whereas  No.  1  cylinder  had 
previously  given  most  trouble.  I  then  concluded,  if  oil  vapor  was 
passing,  it  could  only  be  at  the  gaps  of  the  piston  rings,  since  the  rings 
were  free  to  revolve,  and  the  fact  of  the  pre-ignition  shifting  from  one 
cylinder  to  another  looked  as  if  a  certain  number  of  ring  gaps,  coming 
into  line,  allowed  the  oil  vapor  to  pass  in  that  particular  cylinder. 
Upon  drawing  the  pistons,  four  of  the  six  rings  in  No.  2  cylinder  where 
the  pre-ignition  had  occurred,  were  found  to  have  their  gaps  in  a  verti- 
cal line,  whereas  the  rings  of  the  other  three  pistons  had  their  gaps  fairly 
evenly  distributed.  I  therefore  had  all  piston  rings  pegged. 

On  the  next  run  all  cylinders  ran  dry,  and  the  oil  pressure  had  to  be 
increased  to  10  Ibs.  per  sq.  in.  before  the  cylinders  appeared  to  get  suffi- 
cient lubrication.  Pre-ignition  had,  however,  disappeared,  and  al- 
though the  engine  has  now  run  on  a  good  load  on  seven  separate  days, 
no  further  trouble  has  occurred. 

Later,  since  the  above  was  written  we  have  had  two  full  days'  run 
on  this  engine  on  three-quarters  to  seven-eighths  load  and  she  has  run 
perfectly  with  no  sign  of  pre-ignition." 


452 


PRACTICE  OF  LUBRICATION 


COOLING  OF  GAS  ENGINES 

Cooling  of  all  parts  of  the  engine  that  come  in  contact  with  the 
hot  gases  is  necessary.  Without  adequate  cooling,  unequal  ex- 
pansion and  distortion  of  the  overheated  parts,  excessive  wear, 
and  piston  seizure  would  occur. 

Small  gas  engines  employ  the  thermo-syphon  system,  but 
most  medium  size  and  all  large  gas  engines  employ  pump  circu- 
lation. In  large  gas  engines  provision  is  made  for  adjusting  the 
supply  of  cooling  water  to  the  various  parts  (cylinder  walls, 
piston,  piston  rods,  cylinder  covers,  and  exhaust  valves).  All 
return  water  pipes  are  ca  ried  to  a  central  place  where  the  tem- 
perature and  the  quantity  of  cooling  water  from  each  part  can  be 
controlled.  The  cooling  water,  after  its  return  from  the  various 


Fig.lSSA 


Fig.lSSB 


FIG.   185.— Cooling  tanks. 


parts  is  pumped  through  a  cooling  tower,  cooled  and  again 
pumped  through  the  engine. 

Smaller  engines  employ  cooling  tanks,  which  must  be  so  ar- 
ranged that  the  water  from  one  tank  flows  into  the  bottom  of  the 
next  one  (Fig.  185A).  With  the  arrangement  shown  in  Fig. 
1855  the  water  flow  is  short-circuited  and  the  wate  is  not  prop- 
erly cooled. 

In  the  inlet  and  outlet  pipes  should  be  fitted  thermometers  for 
registering  the  temperature  of  the  cooling  water.  The  average 
temperature  of  the  return  cooling  water  should  be  between' 100° 
and  130°F.  in  large  gas  engines  and  between  100°F.  and  140°F. 
for  smaller  engines.  If  the  outlet  water  from  the  water  jacket 
is  too  high,  the  temperature  of  the  cylinder  wall  will  rise;  the 
oil  film  thins  out,  losing  its  sealing  power  and  the  explosion  gases 
blow  past  the  piston.  If  the  outlet  water  is  much  below  100°F. 
the  cooling  of  the  cylinder  walls  is  too  efficient.  The  oil  film 
becomes  sluggish,  the  oil  spreads  with  difficulty  and  a  great  deal 
of  power  is  lost  in  overcoming  the  oil  drag  on  the  piston.  A  tem- 
perature of  115°F.  to  120°F.  is  therefore  preferable  in  order  to 
insure  good  piston  seal  and  a  free  sliding  motion  of  the  piston. 


GAS  ENGINES  453 

The  cooling  water  must  be  clean,  for  if  impurities  settle  in  the 
water  jacket  the  cooling  of  the  cylinder  walls  and  pistons  (where 
pistons  are  water-cooled)  becomes  defective,  the  temperature 
rises  and  pre-ignition,  caused  by  incandescent  deposits  inside  the 
combustion  chamber,  is  likely  to  occur. 

Where  the  gas  contains  an  excessive  amount  of  sulphur  (large 
gas  engines)  successful  results  have  been  obtained  by  allowing 
the  cooling  water  to  run  through  the  engine  at  a  higher  tempera- 
ture, as  high  as  160°F.  The  higher  temperature  of  the  cooling 
water  minimizes,  or  entirely  prevents,  the  condensation  of  mois- 
ture from  the  expanding  gases  and  thereby  the  formation  of 
sulphurous  acid,  which  would  attack  the  internal  surfaces  of  the 
engine  that  come  in  contact  with  the  gases. 


GAS 

When  using  rich,  highly  inflammable  gas,  such  as  natural 
gas,  the  compression  pressure  at  the  end  of  the  compression 
stroke  must  be  proportionately  low;  otherwise  pre-ignition  will 
occur,  due  to  the  heat  developed  by  compression.  With  weak, 
less  inflammable  gas,  such  as  the  producer  gases,  the  compression 
pressure  can  be  made  much  higher. 

This  is  shown  in  Table  No.  26  which  gives  average  comparative 
heat  values  of  gases  and  corresponding  average  compression 
pressures : 

TABLE  No.  20 

Kind  of  gas 


Natural  gas j      1000  100 

Illuminating  gas itr.  .',i -ii, .•»*!;-* -. ,  .  .         600  120 

Coke  oven  gas I       520  130 


Producer  gases I       130 

Blast  furnace  gas , 100 


150 
190 


Small  and  medium  size  gas  engines  are  operated  by  natural 
gas,  illuminating  or  town  gas,  suction  producer  gas,  or  pressure 
producer  gas.  Large  gas  engines  are  operated  by  blast  furnace 
gas,  coke  oven  gas  or  pressure  producer  gas. 

Natural  Gas. — Natural  gas  is  found  in  the  oil  districts  of  the 
United  States,  Canada,  Russia,  and  Mexico.  It  is  dry  in  its 
natural  state,  with  a  degree  of  purity  that  makes  cleaning 
unnecessary . 


454  PRACTICE  OF  LUBRICATION 

Illuminating  or  Town  Gas. — Illuminating  gas  is  used  practically 
only  for  small  gas  engines.  It  is  made  from  bituminous  coal  by 
dry  distillation.  It  is  free  from  impurities  and  is,  therefore,  an 
excellent  fuel. 

Suction  Producer  Gas. — Suction  producer  gas  is  usually  made 
from  coke,  anthracite  coal,  lignite,  wood  refuse,  etc.  The  engine 
draws  the  gas  from  the  producer  by  suction — hence  the  name 
suction  producer  gas.  Suction  producer  gas  plants  are  used  for 
installations  comprising  one  or  more  engines  with  a  total  power 
not  exceeding  500  H.P. 

Pressure  Producer  Gas. — Pressure  producer  gas  is  made  from 
a  variety  of  fuels,  such  as  bituminous  coal,  lignite,  coke,  anthracite, 
charcoal,  sawdust,  wood  refuse,  etc.  The  gas  is  produced  under 
slight  pressure — hence  the  name  pressure  producer  gas. 

Pressure  producer  gas  plants  are  sometimes  used  for  installa- 
tions as  small  in  size  as  200  H.P.,  but  the  installations  usually 
range  from  400  H.P.  to  2000  H.P.  or  more,  employing  medium 
size  or  large  size  gas  engines. 

Where  bituminous  coal  is  used,  rich  in  tarry  matters,  the  clean- 
ing plant  for  the  gas  must  be  more  elaborate  and  efficient,  and 
therefore  more  costly  than  in  the  case  of  suction  producer  gas 
plants,  which  preferably  use  fuel  free  from  tar. 

Producer  gas,  whether  suction  gas  or  pressure  gas,  should  be 
thoroughly  scrubbed,  cooled  and  cleaned;  but  notwithstanding 
all  precautions  taken  the  gas  always  contains,  besides  moisture, 
more  or  less  impurities,  such  as  soot,  fine  dust  (coke  dust,  ash) 
and  tar,  which  are  carried  into  the  engine  and  interfere  with 
lubrication. 

Blast  Furnace  Gas. — The  blast  furnace  gas  coining  from  the 
blast  furnace  contains  a  great  quantity  of  impurities,  consisting 
of  lime  dust,  fine  iron  oxide,  coke  dust  and  volatile  matter  from 
incomplete  combustion  in  the  blast  furnace,  water  impurities 
from  the  water  used  in  washing  the  gas,  and  a  small  amount  of 
sulphur.  The  quantity  of  impurities  varies  from  12  to  25 
grams  per  cubic  meter  of  gas,  and  is  reduced  in  the  cleaning 
plant  to  0.01  to  0.03  gram  per  cubic  meter.  If  the  impurities 
are  more  than  0.05  gram  per  cubic  meter  the  gas  is  dangerous 
for  the  engines  and  will  cause  deposits  and  excessive  wear  of 
piston  rings  and  cylinder  walls. 

The  gas  is  freed  from  the  dust  and  tarry  impurities  by  either 
the  wet  or  the  dry  cleaning  process.  By  the  latter  process  the 
gas  is  filtered  dry  through  filter  bags  and  is  delivered  in  a  less 
moist  condition  to  the  engines,  so  that  it  is  less  liable  to  de- 
posit dust  in  the  mixing  valves  and  cylinders. 


GAS  ENGINES  455 

Coke  Oven  Gas.  Coke  oven  gas  is  produced  from  bituminous 
coal  during  the  production  of  coke.  A  portion  of  the  gas  is  used 
in  the  coke  oven,  but  the  surplus  gas  can  be  used  for  operating 
gas  engines.  The  coke  oven  gas  contains,  besides  coke  dust,  tar 
and  sulphur. 

Sulphur  in  Coke  Oven  or  Producer  Gas. — Heavy  wear  is  often 
noticed  when  the  gas  is  not  sufficiently  low  in  sulphur  contents. 
The  wear  is  chiefly  on  the  piston  rod,  but  only  on  the  part  of  the 
rod  rubbing  in  contact  with  the  rings  in  the  metallic  packing. 
The  greatest  wear  is  where  the  rod  is  coolest,  i.e.  where  the  water 
enters;  the  wear  is  less  on  the  tail  rod,  where  the  water  leaves 
the  rod  warm.  The  rod  does  not  get  pitted,  but  wears  uniformly, 
maintaining  a  bright  polished  surface,  with  dark  colored  patches 
showing  here  and  there. 

By  allowing  the  cooling  water  to  pass  warmer  through  the 
rods,  the  wear,  as  mentioned  page  453,  is  reduced  or  eliminated. 

If  a  piston  rod  gets  splashed  with  water  from  the  water  dis- 
charge tubes  (outside  the  cylinder)  it  will  wear  rapidly,  if  the  gas 
contains  an  excessive  amount  of  sulphur.  A  water  leak  from  the 
cylinder  head  into  the  metallic  packing  will  have  a  similar  effect. 
In  the  case  of  a  porous  cylinder,  allowing  cooling  water  to  leak 
into  the  cylinder,  sulphur  will  cause  extremely  rapid  wear. 

DEPOSITS 

Deposits  form  in  the  mixing  and  inlet  valves,  in  the  cylinders, 
on  the  piston,  behind  and  between  the  piston  rings,  on  the  ex- 
haust valves,  and  in  the  stuffing  boxes.  In  two-stroke  cycle 
engines  deposits  are  also  formed  in  the  gas  and  air  pumps.  De- 
posits may  arise  from  one  or  several  of  the  following  causes: 
dust  or  dirt  in  the  intake  air,  incomplete  combustion,  impurities 
in  the  gas,  overfeeding  of  oil,  the  use  of  an  unsuitable  oil.  The 
formation  of  deposits  under  certain  conditions  leads  to  preignition 
and  backfiring. 

Intake  air  is  usually  not  filtered,  even  when  the  engines  are 
placed  in  dirty  surroundings.  Impure  intake  air  is  therefore 
a  frequent  cause  of  deposits  in  gas  engines,  regardless  of  the 
kind  of  gas  used.  (See  Examples  Nos.  34,  37  and  39,  pages 
458,  459,  461.)  In  such  cases  a  chemical  examination  will  prove 
the  presence  or  sand,  brick  dust,  lime  dust,  etc.  The  deposit 
will  also  contain  oil  and  partly  decomposed  oil,  due  to  the  oxi- 
dizing action  of  the  impurities  on  the  oil  under  high  temperature 
conditions,  and  there  will  always  be  present  a  percentage  of  iron 
and  iron  oxide,  due  to  wear  of  the  piston  rings  and  cylinder. 


456  PRACTICE  OF  LUBRICATION 

In  large  gas  engines  the  air  should  be  filtered  through  coarse 
canvas  or  similar  material  before  passing  to  a  large  settling 
chamber,  which  will  collect  more  of  the  solid  impurities. 

Incomplete  combustion  will  bring  about  sooty  crumbly  deposits 
and  may  be  due  to  poor  ignition  or  improper  timing  of  the 
valves. 

Impurities  in  the  Gas. — (See  Examples  Nos.  37,  38  and  39.) 

Where  producer  gas  is  in  use,  deposits  may  be  caused  by  such 
impurities  as  ash,  fine  coke  dust,  free  soot  or  tar  passing  into 
the  engine.  All  fuels  contain  ash,  and  a  regular  feeding  of  fuel 
through  the  generator  and  removal  of  clinker  from  the  grates 
are  very  desirable,  because  if  the  grate  is  not  covered  with  a  suffi- 
cient layer  of  fuel,  fine  ash  is  likely  to  be  carried  over  with  the 
gas.  Regular  firing  is  therefore  important,  as  it  prevents  the 
layer  of  fuel  from  getting  too  low. 

Where  coke  is  used,  there  is  no  tar,  but  coke  dust  may  be 
carried  over  in  such  fine  form  that  neither  the  water  trap, 
scrubber,  nor  filter  will  remove  it. 

Where  gas  is  produced  from  anthracite  coal,  tar  and  soot 
may  both  be  carried  over,  although  anthracite  contains  only  a 
small  percentage  of  tar. 

Where  gas  is  produced  from  lignite,  which  contains  more  tar 
and  soot,  the  danger  of  forming  deposits  inside  the  engine  is 
more  pronounced. 

Lignite  also  contains  a  small  percentage  of  sulphur;  this  in 
many  cases  will  cause  a  blackening  of  the  piston  surface,  but 
rarely  causes  serious  trouble. 

Where  gas  is  produced  from  bituminous  coal  which  contains 
a  large  percentage  of  tar,  there  is  greatly  increased  likelihood  of 
the  gas  carrying  soot  and  tar  into  the  engine. 

Coke  oven  gas  and  pressure  producer  gas  contain  some  vola- 
tilized tar  which  cannot,  be  elminated  in  the  producer  plant 
and  which  settles  in  the  gas  inlet  valve  and  mixing  chamber  or 
in  the  gas  pump  (two-stroke  engines).  When  inlet  valves  stick 
they  can  be  " freed"  by  applying  creosote.  The  tar  affects  the 
lubrication,  encouraging  the  formation  of  carbonaceous  deposits. 
It  is  this  formation  of  tar  which  makes  it  necessary  in  suction 
producer  plants  to  employ  coke  or  non-caking  anthracite  coal. 

The  moisture  in  wet  gas,  such  as  the  producer  gases  and  blast 
furnace  gas,  forms  a  paste  with  the  impurities  in  the  air  or  gas, 
thus  providing  a  base  for  the  ready  formation  of  deposits.  The 
impurities  collect  in  the  mixing  and  inlet  valves  and  on  the  internal 
surfaces  of  the  engine  exposed  to  the  gas,  adhering  to  and  con- 
taminating the  oil  film  on  the  piston,  piston  rings  and  cylinder 


GAS  ENGINES  457 

walls.  The  pasty  deposits  in  the  mixing  valve  chambers  in 
time  become  crumbly,  peel  off  and  are  swept  into  the  cylinders, 
causing  excessive  wear,  pre-ignition,  etc. 

In  two-stroke  cycle  gas  engines  moist  gas  will  also  deposit 
the  dust,  in  the  form  of  a  dark  sludge,  in  the  valve  chamber  of 
the  gas  pump.  The  sludge  causes  increased  resistance  in  moving 
this  valve,  with  consequent  sluggish  action  of  the  governor. 

Deposits  arising  from  air  or  gas,  or  both,  always  contain  oil 
and  also  partly  decomposed  oil,  the  latter  due  to  action  of  the 
impurities  on  the  oil  under  high  temperature  conditions. 

Over-feeding  of  Oil. — The  surplus  oil,  fed  to  the  internal  parts, 
burns  and  chars;  it  also  attracts  and  collects  the  impurities  from 
the  gas  and  air,  resulting  in  a  dark  colored  carbonaceous  de- 
posit of  a  harder  or  softer  nature,  depending  upon  the  nature 
of  the  oil  in  use.  Even  with  a  good  quality  oil  in  use,  the  oil 
feeds  should  be  reduced  to  the  exact  amount  required  for  full  and 
efficient  lubrication.  This  will  lead  to  cleaner  lubrication  as 
the  impurities  find  less  oil  to  which  they  can  adhere. 

Deposits  accumulating  behind  the  piston  rings  may  cement 
the  rings  in  their  grooves,  so  that  they  lose  their  elasticity  and 
break  easily.  Heavy  wear  takes  place,  the  oil  film  is  burned  away, 
the  burning  gases  pass  the  piston,  and  in  the  case  of  double  act- 
ing engines  pass  from  one  side  of  the  piston  to  the  other,  igniting 
the  fuel  charge  on  the  opposite  side  and  causing  pre-ignition. 
Increased  oil  feed  will  only  aggravate  the  trouble.  Frequently 
the  stuffing  boxes  in  large  gas  engines  are  overlubricated,  with 
the  result  that  carbon  deposits  are  formed,  causing  the  packing 
rings  to  stick  in  their  grooves.  Wear  follows  and  the  gases  blow 
past  the  rings. 

Pre-ignition. — When  carbon  deposits  or  other  deposits  develop 
inside  the  combustion  chamber,  and  particularly  if  the  water  cool- 
ing is  inefficient,  the  deposits  often  become  incandescent  and  pre- 
ignitions  occur,  causing  abnormally  heavy  strains  on  the  engine. 

But  deposits  are  not  the  only  cause  of  pre-ignition.  Jointing 
material — asbestos,  red  lead — is  often  the  cause  of  this  trouble. 
Pre-ignition  may  also  be  due  to  the  use  of  rich  gas,  for  example, 
town  gas  in  engines  designed  for  suction  gas,  as  the  richer  gas 
ignites  spontaneously  at  a  lower  temperature. 

With  blast  furnace  gas  it  is  difficult  to  prevent  pre-ignition, 
owing  to  the  quantity  of  fine  lime  dust  in  the  gas,  which,  when  it 
settles  inside  the  cylinders,  easily  becomes  incandescent. 

In  large  engines  pre-ignitions  occur  every  2  to  3  hours,  under 
the  most  favorable  conditions,  and  under  unfavorable  con- 
ditions every  few  revolutions. 


458  PRACTICE  OF  LUBRICATION 

Pre-ignitions  may  be  caused  by  the  explosion  gases  leaking  past 
the  piston  rings  from  one  side  of  the  piston  to  the  other.  This 
happens  when  the  rings  are  badly  sealed,  due  either  to  accumulated 
deposits  causing  the  rings  to  be  inflexible  in  their  grooves,  or  to  the 
use  of  too  low  viscosity  lubricating  oil,  or  to  a  furred  up  water 
jacket  (the  oil  film  gets  hot  and  thins  out),  etc. 

'   f       A  FEW  EXPERIENCES 

Example  No.  34.  Dirty  Intake  Air. — The  following  analysis 
of  two  deposits  taken  simultaneously  from  the  piston  indicates 
dirty  intake  air,  which  has  caused  a  great  deal  of  wear  (iron 
oxides).  The  hard  deposit  at  one  time  has  no  doubt  passed 
through  the  stage  represented  by  the  soft  deposit,  the  oil  gradually 
charring  and  hardening  the  mass.  The  oil  in  use  was  a  straight 
mineral  paraffin  base  oil;  had  it  been  an  asphaltic  base  oil,  and 
preferably  compounded,  the  deposit  would  not  have  hardened, 
but  would  have  been  in  the  form  of  a  crumbly  or  greasy  paste. 

Soft  deposit      '       Hard  deposit 


Oil  £&#    iK>>vJ 

34  9  1 

12  1  1 

Volatile  matter  insoluble  in  petroleum 
spirits  .  i 

68% 
33  1  1 

>  66 
54  3 

4% 

Iron  oxides 

28  0% 

30  4% 

Oxides  of  silica  

16% 

1  2% 

Balance  undetermined 

2  4% 

2  0% 

100.0%  100.0% 


It  is  surprising  many  times  to  see  the  lack  of  care  in  not  pro- 
viding gas  engines  with  reasonably  clean  intake  air. 

Example  No.  35.  A  Curious  Case  of  Spontaneous  Ignition. — 
An  old  gas  engine  of  about  25  H.P.  with  leaky  piston  rings  and 
with  a  temperature  of  about  200°F.  in  the  water  jacket,  was 
using  a  heavily  compounded  oil.  The  gudgeon  pin  and  piston 
were  very  hot.  The  engine  was  in  a  wooden  shed  close  to  saw 
benches,  and  as  the  door  of  the  shed  was  always  open  a  consider- 
able amount  of  wood  dust  was  always  entering  the  engine  room. 
In  particular  where  the  crank  pin  had  thrown  the  oil  on  the  side 
of  the  shed,  the  dust  and  oil  had  formed  a  layer  a  quarter  of  an 
inch  thick.  One  day  the  heat  of  the  piston  caused  the  oil  to 
ignite,  throwing  out  a  flame  sufficiently  long  to  reach  the  layer 
of  oil  on  the  side  of  the  shed,  which  it  also  ignited. 

The  ignition  took  place  in  the  hollow  part  of  the  piston  whore 


GAS  ENGINES 


459 


the  gudgeon  pin  end  of  the  counseling  rod  works.  The  saw-dust 
had  accumulated  in  the  hollow  of  (he  piston  and  was  saturated 
with  the  highly  compounded  oil  in  use.  As  time  went  on  this  oil 
became  gummy,  oxidising  more  and  more,  and  as  the  heat  from 
the  piston  increased,  owing  to  the  gas  engine  being  heavily 
loaded,  the  oxidizing  effect  raised  the  temperature  up  to  ignition 
point. 

Example  No.  36.  Bad  Alignment. — A  60  H.P.  gas  engine  was 
continually  breaking  piston  rings;  the  back  piston  ring  could  not 
be  lubricated  and  the  piston  could  therefore  never  be  kept  tight. 
The  makers  had  overhauled  the  engine  time  and  time  again 
without  locating  the  cause;  a  special  attachment  was  fitted  which 
lubricated  the  back  ring,  but  the  breakages  continued.  Finally, 
the  seat  of  the  trouble  was  discovered;  the  cylinder  was  out  of 
line  with  the  crank  pin  to  the  extent  of  %  Q  inch,  which  caused 
a  great  pressure  between  the  piston  rings  and  the  liner. 

Example  No.  37.  Deposit  Caused  by  Impurities  in  the  Gas.— 
Several  large  blast  furnace  gas  engines  of  the  Cockerill  type 
(double-acting,  four-stroke,  tandem  engines,  1500  H.P.)  were 
wearing  badly  owing  to  deposits  which  continued  to  develop  in- 
side the  cylinders.  The  cylinder  wear  had  averaged  0.7  mm.  per 
annum,  as  compared  with  the  normal  wear  for  large  blast  furnace 
gas  engines  which  ranges  from  0.3  to  0.5  mm.  per  annum. 

Samples  of  deposit  were  obtained  from  the  following  points 
and  analyzed: 


Piston  surface 
outside  the 
rings,  % 

Piston  surface  j  Inside   of 
between  the        piston 
rings,  %          rings,  % 

Piston 
rod,  % 

Oil  and  moisture  Traces 
Volatile  matter  insoluble  in  pe- 
troleum spirit  34  .  9 

:••. 
Traces 

43.3 
12.1 
22.4 

22.2 

Traces 

37.8 
17.7 
11.2 

33.3 

Traces 

56.9 
12.5 
10.8 
6.4 
10.2 

3.2 

Silicates  and  oxides  of  silica.  ...           16.6 
Iron  oxides  .  .                                  '         18  3 

Aluminium  oxides  57 

Calcium  oxides  .                 12  6 

Balance,  containing  magnesium 
oxides  and  traces  of  other  me- 
tallic salts  11.9 

100.0 

100.0 

100.0      100.0 

All  the  deposits  were  hard,  granular  and  black,  and  their  com- 
position shows  that  the  gas  is  mainly  responsible  for  their  forma- 
tion, the  dust  contents  in  the  gas  ranging  from  0.025  to  0.035 


460 


PRACTICE  OF  LUBRICATION 


grammes  per  cubic  metre.  The  lubricating  oil  in  use  was  a  deep 
red  straight  mineral  paraffin  base  oil  containing  filtered  cylinder 
stock  which  carbonized  and  caused  the  deposit  to  bake  into  hard 
crusts.  It  is  possible  that  some  of  the  dust  came  with  the  intake 
air,  as  the  intake  air  pipes  were  placed  with  their  ends  turned  up, 
so  that  the  dirt  and  dust  had  free  access.  Besides,  on  this  par- 
ticular side  of  the  power  house  were  situated  the  stores  of  coal, 
coke,  etc.  It  would  have  been  better  had  the  air  pipes  been 
placed  on  the  opposite  side  of  the  power  house,  taking  the  air 
through  large  settling  chambers,  fitted  with  suitable  filter  screens. 
Fig.  186  shows  a  good  arrangement  for  preventing  impurities 
from  entering  a  gas  engine  with  the  intake  air. 


1  Air  Pit 

2  Filter  Screens 

3  Air  lutake  Pipe 


FIG.   186. — Filtering  intake  air. 

Example  No.  38,  Tarry  Deposits.— Two-stroke  gas  engines 
employing  coke  oven  gas  are  often  troubled  with  tarry  deposits, 
which  accumulate  in  the  gas  pumps,  on  the  inlet  valves  and  inside 
the  cylinders. 

A  500-H.P.  Koerting  engine  had  to  be  dismantled  every  four 
weeks  to  clean  away  the  deposits.  A  straight  mineral  dark 
red  paraffin  base  oil  was  used,  fed  through  sight  feed  drop  oilers. 
A  mechanically  operated  lubricator  was  installed  in  order  to 
bring  about  a  regular  feed,  so  that  a  minimum  oil  consumption 
could  be  established.  At  the  same  time  an  oil  made  chiefly 'from 
asphaltic  base  mineral  oil  and  compounded  with  7  per  cent,  of  nut 
oil  was  introduced  with  most  remarkable  results,  it  being  found 
possible  to  operate  the  engine  for  five  months  before  it  was  con- 
sidered desirable  to  clean  out  the  deposit.  In  addition  it  was 
found  that  the  engine  now  started  quite  easily  on  compressed 
air,  whereas  with  the  previous  oil  it  was  necessary  to  "  mo  tor" 
the  generator  when  starting. 


GAS  ENGINES  461 

Example  No.  39.  Deposit  Due  to  Water  Leakage. — In  the 
case  of  seven  800-H.P.  blast  furnace  gas  engines,  single  cylinder 
engines  with  open-ended  trunk  pistons,  a  dark  brown,  almost 
black,  oily  deposit  was  continuously  working  its  way  out  from 
the  cylinders.  A  sample  showed  the  following  analysis: 

Oil • 35.3  per  cent. 

Water 8 . 2  per  cent. 

Iron,  iron  oxides  and  silica 21.9  per  cent. 

Volatile    matter   insoluble    in   petroleum 

spirit 34 . 6  per  cent. 

The  water  came  from  the  leaky  cooling  pipe  connections;  the 
silica  came  in  with  the  intake  air  or  the  gas  and  caused  heavy 
wear,  the  action  being  accentuated  in  the  presence  of  water. 

OIL 

General. — The  frictional  losses  in  a  small  or  medium  size  gas 
engine  range  from  15  per  cent,  to  30  per  cent.,  in  large  gas  engines 
from  10  per  cent,  to  20  per  cent,  of  the  rated  horse  power,  this 
loss  being  constant  and  independent  of  the  actual  engine  load. 
It  is  easy  to  waste  from  5  per  cent,  to  10  per  cent,  of  the  engine 
power  in  unnecessary  friction  by  using  unsuitable  lubricating  oil 
or  an  inefficient  lubricating  system. 

SMALL  AND  MEDIUM  SIZE  HORIZONTAL  GAS  ENGINES 

Piston  Lubrication. — The  piston  of  the  gas  engine  is  the  most 
vital  part  from  a  lubricating  standpoint.  With  impure  gas  or 
unsuitable  oil  or  overfeeding,  deposits  develop  on  the  piston 
head  and  behind  the  piston  rings,  and  will  appear  in  the  form 
of  a  black,  oily  coating.  These  deposits  soon  cause  the  piston 
rings  to  cement  in  their  grooves;  the  gases  blow  past  the  piston; 
excessive  friction  and  wear  take  place  on  the  piston  rings  and  on 
the  cylinder  walls. 

It  is  important  that  the  oil  shall  have  a  suitable  viscosity. 
If  an  oil  of  too  heavy  viscosity  is  used,  it  does  not  spread  easily 
over  the  piston  surface.  The  friction  is  high  owing  to  the  heavy 
oil  drag  on  the  piston,  and  impurities  in  the  gas  or  air  will  cling 
to  the  heavy  oil  and  bake  into  crust-like  deposits. 

In  the  United  States  practically  all  large  gas  engines  are 
lubricated  with  oils  which  are  -highly  filtered  cylinder  stock, 
having  viscosities  ranging  from  125"  to  175"  Saybolt  at  210°F. 

The  very  same  types  of  engines  are  lubricated  successfully 
in  Eu  ope  with  oils  having  Saybolt  viscosities  ranging  from  45" 
to  70"  at  212°F.  It  is  practically  certain  that  the  American 
engines  would  operate  better,  with  less  friction,  easier  starting 


462  PRACTICE  OF  LUBRICATION 

and  less  carbon  deposit,  if  they  used  oils  more  in  line  with  Euro- 
pean practice. 

If  an  oil  of  too  light  viscosity  is  used,  it  will  break  down  under  the 
influence  of  the  high  temperature  in  the  cylinder;  it  will  loose  its 
sealing  power,  causing  excessive  friction  and  wear.  Carbonace- 
ous deposits  are  formed  which  on  account  of  the  wear  will  be 
found  to  contain  a  large  percentage  of  iron  and  iron  oxides. 

Bearing  Lubrication. — Main  bearings  usually  give  no  trouble; 
it  is  bad  practice  to  add  oil  to  ring  oiled  main  bearings  daily. 
The  bearings  do  not  run  cooler,  but  the  oil  is  wasted,  overflowing 
from  the  bearing  ends. 

The  bearing  reservoirs  should  be  emptied,  cleaned,  and  re- 
charged at  regular  intervals,  from  3  to  6  months,  depending  upon 
the  purity  (absence  of  dust)  of  the  air  in  the  engine  room. 

The  crank  pin  is  a  very  important  part  of  the  engine  as  it 
transmits  the  power  from  the  piston  to  the  main  shaft.  Occa- 
sionally, a  heavy -bodied  oil  is  required  for  lubricating  the  crank 
piri  of  medium  size  engines  owing  to  the  heavy  crank  pin  bear- 
ing pressures.  As  this  oil  may  be  too  heavy  in  body  for  the 
cylinder  lubrication,  two  different  oils  are  sometimes  used, 
although  usually  one  oil  is  used  throughout. 

The  gudgeon  or  wrist  pin  requires  particular  care  in  lubrication 
as  it  is  located  in  the  interior  of  the  heated  hollow  trunk  piston, 
where  it  is  subjected  to  high  temperature.  The  pressures  on  the 
wrist  pin  are  high,  and,  as  the  oscillating  motion  of  the  connect- 
ing rod  is  slight,  the  oil  spreads  with  difficulty  over  the  bearing 
surfaces.  Consequently,  the  lasting  and  lubricating  properties 
of  the  oil  used  are  very  important. 

The  blackened  waste. oil  coming  from  the  piston  and  wrist  pin 
in  small  and  medium  size  engines  should  be  arrested  by  a  division 
plate  (see  Fig.  179,  page  441)  and  drained  away  so  that  it  will 
not  run  into  the  crank  pit  and  contaminate  the  oil  coming  from 
the  crank  pin. 

LARGE  GAS  ENGINES 

Piston  Lubrication. — Owing  to  the  large  diameter  of  the  pis- 
tons, it  is  of  the  greatest  importance  that  the  oil  be  introduced 
direct  to  the  piston  at  several  points,  and  in  such  a  manner  that 
the  correct  amount  of  oil  is  delivered  to  the  piston  at  the  correct 
moment,  positively  and  regularly.  Incorrect  methods  of  lubrica- 
tion, or  lubricators  that  cannot  be  relied  upon  to  feed  the  oil  in  the 
best  manner,  mean  excessive  oi]  consumption ;  the  waste  of  oil  is  less 
important  than  the  fact  that  the  impurities  in  the  gas  adhere  to  the 
surplus  oil,  which  leads  to  the  formation  of  carbonaceous  deposit  s. 


GAS  ENGINES  463 

Stuffing  Box  Lubrication. — When  an  oil  too  low  in  viscosity 
is  used  it  cannot  seal  the  packing  properly,  and  allows  gas  to 
blow  through  the  stuffing  boxes.  The  gas  burns  and  chars  the 
oil,  causing  heavy  wear  and  the  formation  of  deposits.  The 
action  of  the  gas  is  extremely  erosive,  cutting  grooves  in  the 
piston  rod  and  shortening  the  life  of  the  metallic  packing.  The 
gas  escaping  from  the  stuffing  boxes  into  the  engine  room  is  very 
poisonous. 

It  is  quite  usual  to  find  that  the  oil  is  fed  to  the  stuffing  boxes 
by  means  of  sight  feed  drop  oilers  and  that,  therefore,  a  great 
deal  more  oil  is  used  than  when  the  stuffing  boxes  are. lubricated 
by  means  of  a  mechanically  operated  lubricator.  It  is  very 
important  that  the  lubrication  of  the  stuffing  boxes  should  be 
kept  clean  and  economical.  Excessive  oil  feed  means  formation 
of  carbon  deposit,  excessive  friction  and  wear,  accentuated  by 
continuous  "  bio  wing"  of  the  glands. 

Where  the  stuffing  boxes  are  worn  and  blowing  takes  place, 
they  should  be  put  in  good  order  at  the  earliest  opportunity, 
although  as  a  temporary  arrangement  an  oil  heavier  in  body  may 
be  used  in  order  to  seal  the  packing  and  prevent  blowing.  Satis- 
factory operation  of  the  stuffing  boxes  is  perhaps  a  more  difficult 
problem  from  a  lubricating  point  of  view  than  any  other  part  of 
the  engine;  it  pays,  therefore,  to  give  special  attention  to  select- 
ing the  correct  oil  for  their  lubrication  and  applying  the  oil  in 
the  best  manner,  using  it  as  economically  as  possible. 

Only  fresh  oil  should  be  used  for  lubrication  of  stuffing  boxes, 
pistons,  valves,  etc.  Any  waste  oil  that  may  be  collected  from 
underneath  the  stuffing  boxes,  valve  spindles,  etc.  may  be  treated 
in  a  heated  separating  tank  and  filter,  after  which  the  oil  can  be 
used  for  less  important  work,  but  it  should  not  be  used  on  the 
gas  engine  itself,  as  it  is  usually  very  dirty. 

External  Lubrication. — The  circulation  system  in  large  gas 
engines  should  preferably  contain  not  less  than  100  gallons 
of  oil,  in  order  to  give  the  oil  a  chance  to  rest  and  separate  from 
the  impurities  that  may  enter  the  system.  The  oil  is  in  constant 
circulation,  exposed  to  the  effect  of  air  and  more  or  less  water 
which  leaks  in  from  the  cooling  system  or  from  the  water  cooled 
main  bearings.  The  action  is  very  similar  to  what  takes  place 
with  oil  in  a  steam  turbine,  only  the  effect  is  less  marked  owing 
to  the  temperatures  and  speeds  being  lower  than  in  turbines, 
and  the  circulation  less  rapid. 

Unsuitable  oil  may  throw  down  deposits  of  various  kinds  which 
are  liable  to  accumulate  in  the  most  dangerous  places,  namely, 
the  oil  passages  inside  the  main  bearings  and  crank  pin,  and  may 
cause  dangerous  heating  of  the  bearings. 


464  PRACTICE  OF  LUBRICATION 

Leakayc  of  water  into  the  oil  system  is  a  source  of  great  annoy- 
ance and  often  produces  emulsion.  The  life  of  the  oil  is  much 
reduced,  and  wear  of  crank  pins  and  crosshead  pins  is  increased. 
It  is  almost  impossible  to  keep  all  water  out  of  the  system,  but 
leakage  may  be  largely  overcome  by  careful  attention  to  packing 
and  joints  of  the  cooling  water  inlet  and  outlet  pipes. 

In  view  of  the  unfavorable  influence  of  water  in  the  circula- 
tion system,  any  accumulation  of  water  and  impurities  should  be 
carefully  drained  away  at  frequent  intervals.  Where  a  great 
many  impurities  enter  the  system  the  oil  or  part  of  it  should 
continuously  pass  through  a  filter.  As  an  alternative,  from  two  to 
six  gallons  of  oil  should  be  removed  every  day  for  treatment  in  a 
steam  heated  separating  tank,  and  afterwards  in- a  good  filter. 
The  purified  oil  should  be  returned  to  the  circulation  system  at 
the  same  time  that  a  corresponding  quantity  of  oil  is  removed 
from  the  system  for  treatment.  When  the  oil  tank  capacity 
in  the  system  is  small,  this  practice  is  particularly  desirable.  In 
this  way  the  vitality  of  the  oil  is  kept  at  as  high  a  standard  as 
possible,  and  the  life  of  the  oil  is  greatly  lengthened. 

Circulation  oils  should  preferably  be  used.  Such  oils  under 
reasonably  good  conditions  of  service  are  practically  indestruc- 
tible and  under  adverse  conditions  (air,  water,  impurities)  they 
are  not  so  liable  as  other  oils  to  emulsify  or  throw  down  deposits. 

Vertical  Gas  Engines. — Unsuitable  oil  (easily  oxidized)  will 
throw  down  deposits  of  various  kinds  which  are  liable  to  accumu- 
late in  dangerous  places,  such  as  the  oil  passages  inside  the  main 
bearings,  crank  pins  and  connecting  rod.  This  may  result  in 
reduction  of  oil  feed  to  some  parts  of  the  engine;  the  bearing 
surfaces  of  the  parts  affected  will  overheat  and  may  be  partially 
or  wholly  destroyed. 

Owing  to  the  high  speed  at  which  vertical  gas  engines  operate, 
it  is  of  very  great  importance  that  the  correct  oil  be  used  in  the 
crank  chamber,  which  will  give  continued  perfect  service,  not- 
withstanding the  severe  conditions  of  speed  and  temperature  to 
which  the  oil  is  exposed.  Consideration  must  be  given  to  the 
temperature  of  the  oil  in  circulation,  as  with  a  high  oil  temperature 
it  is  necessary  to  use  an  oil  heavy  in  body. 

It  must  also  be  kept  in  mind  that  the  lubrication  requirements 
of  the  cylinders  of  a  vertical  gas  engine  are  different  from  the 
lubrication  requirements  of  the  external  moving  parts,  enclosed 
in  the  crank  chamber.  In  larger  size  vertical  gas  engines  which 
are  constructed  with  a  distance  piece  between  the  cylinders  and 
the  crank  chamber,  the  lubrication  of  cylinders  and  bearings  is 
carried  out  by  means  of  two  separate  and  distinct  systems,  viz. 


GAS  ENGINES  465 

mechanically  operated  lubricator  for  the  cylinders  and  usually 
force  feed  circulation  for  the  bearings.  For  bearing  lubrication 
of  such  engines,  circulation  oils  should  preferably  be  used. 

The  oil  for  the  cylinders  should  preferably  have  non-carboniz- 
ing properties  and  can  be  chosen  entirely  with  a  view  to  suit  the 
cylinders. 

Where  engines  have  cylinders  with  trunk  pistons  mounted 
directly  on  top  of  the  crank  chamber,  and  where  all  parts, 
including  the  pistons,  are  lubricated  from  a  common  system 
of  lubrication,  one  grade  of  oil  must  be  used  throughout;  so  that 
it  becomes  necessary  to  select  an  oil  possessing  such  qualities  as 
will  enable  it  to  meet  the  double  requirements  of  cylinder  and 
bearing  lubrication  as  perfectly  as  possible. 

For  piston  cooling  of  large  vertical  engines,  cooling  oil  is  pref- 
erably used,  as  it  is  difficult  to  guard  against  leakage,  and  water 
would  cause  emulsification  of  the  oil  in  the  crank  chamber. 

Circulation  oils  should  preferably  be  used  as  cooling  oils  and 
should  preferably  be  of  light  or  medium  viscosity,  as  the  lower 
the  viscosity  the  better  is  the  cooling  effect;  but  when  joints 
are  leaking  a  viscous  oil  may  be  preferred,  as  it  does  not  leak  so 
readily  and  in  mixing  with  the  crank  chamber  oil  has  less  thin- 
ning effect  on  the  oil  in  circulation  than  a  light  viscosity  cooling 
oil. 

OIL  CONSUMPTION 

In  all  small  or  medium  size  gas  engines,  the  oil  is  frequently  fed 
irregularly,  and  a  great  deal  of  oil  is  wasted,  either  because  of  the 
lubricators  themselves  or  because  it  is  not  possible  to  give  the 
engines  the  same  close  attention  and  supervision  as  in  large 
power  plant  installations.  Frequently,  the  practice  is  to  use 
plenty  of  oil  all  around  the  engine,  collect  the  waste  oil  and  use 
it,  after  having  filtered  it  more  or  less  efficiently,  for  shafting 
and  machinery  in  the  works.  This  practice  is  false  economy. 

Fresh  oil  only  should  be  used  for  piston  lubrication. 

Waste  oil  from  the  bearings  should  be  collected,  and  if  filtered 
in  a  good  filter  it  can  be  used  again  on  the  bearings;  good  quality 
oil  can  be  used  over  and  over  again  almost  indefinitely,  producing 
great  economy.  If  the  waste  oil,  whether  filtered  or  otherwise, 
is  used  for  the  machinery  in  the  plant,  the  gas  engine  attendant 
feels  that  he  need  not  use  the  oil  economically,  as  the  oil  is  made 
use  of  afterwards;  and  the  men  using  the  waste  oil  feel  that  it  is 
only  waste  oil  and  in  consequence  use  it  extravagantly. 

Using  the  waste  oil  in  the  engine  room  and  keeping  the  gas 
engine  attendant  responsible  for  his  oil  consumption  ensures  the 

30 


406  PRACTICE  OF  LUBRICATION 

best  results;  besides,  in 'many  cases  it  will  be  found  that  much 
better  results  can  be  obtained  on  the  machinery  and  shafting  in 
the  plant  by  using,  instead  of  the  filtered  waste  oil,  one  or  several 
oils,  specially  selected  to  suit  the  various  conditions  in  the  plant. 

For  small  gas  engines  up  to  50  H.P.  the  oil  consumption  will 
range  from  2  to  5  grains  per  B.H.P.  hour. 

For  medium  size  gas  engines  between  100  and  500  B.H.P. 
the  oil  consumption  will  range  from  1  to  3  grams  per  B.H.P.  hour, 
being  lower  for  the  larger  engines. 

For  vertical  gas  engines  the  consumption  ranges  from  1.5  to  3.0 
grams  per  B.H.P.  hour,  depending  largely  upon  the  condition  of 
piston  rings,  oil  pressure,  or  oil  level,  etc. 

For  large  gas  engines  the  oil  consumption  ranges  from  0.6  to  2.0 
grams  per  B.H.P.  hour  and  averages  1.0  grams  per  B.H.P.  hour. 
This  consumption  is  divided  among  cylinders,  piston  rod  pack- 
ings and  bearings,  approximately  in  the  ratios  of  35  per  cent., 
15  per  cent,  and  50  per  cent,  respectively. 

SELECTION  OF  OIL 

Before  selecting  the  correct  grade  of  oil  in  order  to  secure 
perfect  lubrication  it  is  necessary  to  consider  carefully  a  number 
of  influencing  factors,  such  as  the  quality  of  the  gas,  the  piston 
clearance,  number  of  piston  rings,  whether  pegged  or  not,  whether 
the  whole  weight  of  the  piston  is  supported  by  external  means 
(large  gas  engines),  or  whether  the  weight  of  the  piston  is  slid- 
ing on  tl>e  bottom  of  the  cylinder,  the  temperature  of  the 
water  jacket,  the  method  of  lubrication,  also  whether  there  are 
any  mechanical  or  operating  conditions  which  call  for  special 
consideration. 

The  object  of  lubrication  of  gas  engines  is  to  provide  clean 
and  efficient  lubrication  of  all  parts:  clean,  because  if  the 
oil  film  is  dirty  or  blackened  with  carbonized  oil  or  with  impurities 
from  the  gas  or  dirty  intake  air,  one  cannot  possibly  expect  good 
lubrication;  efficient,  meaning  that  lubrication  is  not  only  clean, 
but  that  the  oil  is  of  the  correct  quality  and  body  to  produce  as 
complete  a  film  as  possible  and  reduce  the  total  loss  in  friction  to 
a  minimum. 

To  show  how  important  it  is  not  to  allow  mere  guess  work  to 
determine  the  grade  of  oil  to  be  used,  some  of  the  influencing 
factors  mentioned  above  are  commented  upon  in  the  following : 

The  Quality  of  the  Gas. — Illuminating  gas  and  natural  gas  are 
always  clean  and  dry,  which  qualities  are  favorable  to  good  lubri- 
cation. Occasionally  producer  gas,  particularly  in  large  in- 


GAS  ENGINES  467 

stalliitions,  may  be  said  to  be  fairly  clean  and  dry.  For  engines 
employing  such  gas,  straight  mineral  oils  of  medium  or  heavy 
viscosity  may  be  used. 

It  is  probable  that  most  users  of  producer  gas,  whether  suction 
or  pressure  producer  gas,  whether  large  or  small  plants,  would 
always  answer  the  question  as  to  whether  the  gas  was  pure,  in 
the  affirmative.  It  is  a  fact,  however,  that  the  gas  from  practi- 
cally all  producer  gas  plants  is  fairly  moist  and  contains  fine  im- 
purities, of  a  tarry  and  a  dusty  nature,  which  in  time  accumulate 
inside  the  gas  engine  cylinder,  producing  carbonaceous  deposits. 

When  the  gas  contains  an  excessive  amount  of  impurities  or 
moisture,  it  will  be  found  that  pale  colored  compounded  oils 
will  show  marked  superiority  over  dark  colored  straight  mineral 
oils  as  regards  clean  lubrication.  The  fixed  oil  contains  oxygen 
which  burns  the  carbon, .  and  the  result  is  -that  the  deposits  are 
prevented  from  caking  and  the  amount  of  carbonaceous  deposit 
formed  is  considerably  reduced,  whereas  straight  mineral  oils 
will  frequently  fail  to  give  satisfaction.  ' 

Another  advantage  of  using  a  compounded  oil  is  the  easier 
starting  of  the  engine.  When  the  engine  stops,  the  piston  is  hot 
and  the  oil  film,  when  the  movement  of  the  piston  ceases,  is 
practically  squeezed  out.  Experience  proves  that  the  presence 
of  animal  or  vegetable  oil  helps  to  retain  a  better  oil  film,  which 
makes  starting  of  the  engine  easier. 

In  Germany  15  per  cent,  to  20  per  cent,  of  kerosene  is  fre- 
quently mixed  with  the  lubricating  oil  for  the  cylinders  of  large 
gas  engines.  The  kerosene  has  a  cleansing  effect  when  the  gas 
centains  a  large  amount  of  impurities. 

Piston  Clearance. — The  larger  the  engine  the  greater  will  be 
the  piston  clearance,  so  that  larger  size  engines  require  an  oil 
heavier  in  viscosity  than  smaller  engines,  in  order  to  completely 
seal  the  piston  and  prevent  "  bio  wing."  The  number  and  posi- 
tion of  the  piston  rings  are  also  important  in  this  respect, 
particularly  whether  they  are  pegged  (which  is  customary)  or 
otherwise.  If  the  piston  rings  are  few  and  not  pegged,  a  heavier 
viscosity  oil  is  required  than  with  a  greater  number  of  pegged 
piston  rings,  the  effect  of  the  pegging  being  that  the  rings  wear 
to  a  fit  in  the  cylinder  and  are  easier  to  seal. 

A  heavy  viscosity  is  also  required  for  engines  with  worn  pistons 
or  cylinders.  Although  it  would  be  better  in  most  cases  to 
rebore  the  cylinder  and  fit  a  new  piston,  yet  circumstances  may 
make  it  desirable,  at  any  rate  as  a  temporary  arrangement,  to 
use  a  heavy  viscosity  oil  until  such  time  as  the  engine  is  put  in 
order,  when  the  correct  lighter  viscosity  oil  can  be  used. 


468  PRACTICE  OF  LUBRICATION 

Cooling  Water. — If  the  cooling  water  leaves  the  cooling  water 
jacket  at  a  temperature  much  above  140°F.  the  cooling  of  the 
cylinder  walls  will  be  inefficient  and  the  high  temperature  will 
thin  the  oil,  so  that  this  condition  may  demand  an  oil  of  heavy 
body.  In  the  same  way,  if  the  cooling  water  leaves  the  engine 
at  too  low  a  temperature,  say,  below  90°F.,  this  condition  may 
demand  the  use  of  an  oil  of  light  body. 

Water  cooling  of  large  pistons  means  that  smaller  piston  clear- 
ances can  be  employed  and  therefore  favors  the  use  of  lower 
viscosity  oils.  This  is  the  reason  why  large  gas  engines  can  be 
so  satisfactorily  lubricated  with  medium  viscosity  oils. 

The  piston  friction  is  much  influenced  by  the  temperature  of 
the  water  jacket.  On  this  subject  Prof.  Bertram  Hopkinson 
gives  in  reference  to  small  gas  engines  some  interesting  data, 
recorded  in  " Mechanical  World"  for  September  6th,  1895.  He 
concludes : 

"The  saving  in  consumption  when  the  engine  is  running  light  may 
be  as  much  as  30  per  cent,  but  at  full  load  it  is  very  small,  and  in  some 
cases  the  consumption  per  brake  horse  power  is  increased  with  a  hot 
jacket.  This,  however,'  depends  to  a  great  extent  upon  the  design  of 
the  engine.  The  great  economy  in  consumption,  when  the  engine  is 
running  light  with  a  hot  cylinder,  is  due  to  a  decrease  of  friction  be- 
tween the  piston  and  liner." 

From  these  experiments  the  conclusion  may  be  drawn  that 
gas  engines  when  running  light  should  preferably  operate  with 
hot  cooling  water,  or,  if  this  condition  is  permanent  a  lighter 
viscosity  oil  will  have  the  same  effect  with  normal  water  tem- 
perature, as  regards  bringing  about  low  friction  losses. 

Method  of  Lubrication. — When,  due  to  the  method  of  lubri- 
cation or  other  reasons,  the  oil  consumption  for  internal  lubri- 
cation is  high,  say  more  than  1.5  grams  per  B.H.P.  hour, 
particular  attention  must  be  given  to  selecting  an  oil  with  "  non- 
carbonizing"  properties.  When  the  oil  consumption  is  low  this 
point  is  of  less  importance.  "  Non-carbonizing  "  oil  means  pale 
colored  " non-par affinic "  base  (i.e.,  asphaltic  or  naphthenic) 
oils,  preferably  compounded. 

All  distilled  lubricating  oils  produce  less  carbon  than  undistilled 
oils — cylinder  stocks — and  filtered  cylinder  oils  produce  less 
carbon  than  dark  cylinder  oils.  Heavy  viscosity  gas  engine  oils 
should  therefore  contain  little  or  no  cylinder  stock,  if  non-car- 
bonizing qualities  are  required.  If  cylinder  stock  is  required  to 
give  the  desired  high  viscosity,  the  distilled  oil  used  for  blending 
should  be  as  viscous  as  possible  in  order  to  reduce  the  amount  of 
cylinder  stock  required. 


GAS  ENGINES 


469 


In  medium  size  yas  engines  the  tendency  is  towards  using  sepa- 
rate oils  for  internal  and  external  lubrication,  as  the  bearing 
requirements  call  for  oils  which  will  stand  great  pressure  and  give 
a  good  cushioning  effect  in  the  crank  pin  bearings.  Such  oils  are 
preferably  mixtures  containing  filtered  cylinder  stock,  whereas 
for  internal  lubrication  a  minimum  of  filtered  cylinder  stock  is 
desirable,  as  above  mentioned. 

The  main  bearings,  being  ring  oiled,  are  of  course  best  served 
by  a  pure  mineral  oil.  Straight  mineral  oils  are  required  for 
large  gas  engines  externally,  preferably  circulation  oils  in  order 
to  avoid  as  much  as  possible  trouble  from  emulsification. 

In  vertical  gas  engines,  where  no  water  gets  into  the  crank 
chamber,  circulation  oils  are  not  absolutely  needed;  the  oils  may 
bo  chosen  chiefly  with  a  view  to  suiting  the  piston  conditions, 
and  of  course  the  crank  chamber  temperatures. 

For  splash  lubrication  the  oil  must  not  be  too  viscous,  as  it 
will  then  only  splash  and  distribute  itself  with  difficulty. 

When  compounded  oils  are  used  in  enclosed  vertical  gas  en- 
gines, the  compound  must  be  a  sweet,  non-gumming  oil,  either 
nut  oil  or  high  quality  lard  oil  made  from  corn-fed  pigs;  lard 
oil  from  distillery  fed  pigs  oxidizes  and  gums,  even  if  it  is  free 
from  acid. 

In  Table  No.  27  are  given  viscosity  figures  for  four  gas  engine 
oils,  which  may  be  either  straight  mineral  or  compounded  with 
from  6  per  cent,  to  10  per  cent,  of  fixed  oil;  in  the  latter  case  a 
"c"  is  added  to  the  No.  of  the  oil.  The  specifications  for  cir- 
culation oils  Nos.  1,  2  and  3  will  be  found  on  page  236. 

The  Lubrication  Charts  Nos.  15  and  16  give  general  recom- 
mendations for  oils  suitable  for  the  main  types  of  gas  engines. 

TABLE  No.  27 


Saybolt  viscosity 

at 

Grade  of  oil 

__  

104°F. 

212°F. 

Gas  engine  oil  No.  1  or  Ic ..I  175"  38" 

Gas  engine  oil  No.  2  or  2c i  300"  45" 

Gas  engine  oil  No.  3  or  3c '  400"  56" 

Gas  engine  oil  No.  4  or  4c 650"  70" 


470 


PRACTICE  OF  LUBRICATION 


LUBRICATION  CHART  No-  15 
FOR  HORIZONTAL  GAS  ENGINES 


Grades    of    gas  engine 
oil  recommended 


Quality  of  gas 


'Dry  and 

clean 

Moist  and 
impure 

4L  LUBRICATION: 

ize.  . 

1  or  2 

! 

lc  or  2e 

SmaU  Size. 

Medium  Size. 

*  Up  to  80  H.P.  per  cylinder,  piston  not  water  cooled 
80-150  H.P.  per  cylinder,  piston  not  water  cooled 


2c 
3c 


With  worn  cylinders,  or  very  hot  water  jacket.  .  .     3  or  4    j  3c  or  4c 


*  NOTE:  The  dividing  line  with  small  piston  clearances 
may  be  as  high  as  120  H.P.  with  large  piston  clear- 
ances as  low  as  50  H.P.  per  cylinder.  Oils  Nos.  31 
and  3c  to  be  used  above  the  dividing  line,  Oils  Nos. 
2  and  2c  below  the  line. 


Large  Size. 
Internal 

4-stroke  cycle,  300  to  750  H.P.  per  cylinder 

For  stuffing  boxes  only,  if  not  sealed  properly  by 

2  or  2c 

4-stroke  cycle,  750  to  1500  H.P.  per  cylinder. .  . 

2-stroke  cycle,  all  sizes 

For  gas  and  air  pumps  only 


2c 


3  or  4  I  3c  or  4c 
3  or  4  I  3c  or  4c 
3c  or  4c 
2c  or  3c 


1  or  2       lc  or  2c 


3  or  4 
2c  or  3c 


EXTERNAL  LUBRICATION: 

Small  Size. 

Medium  Size.     Oils  Nos.  2,  3  or  4  or  Bearing  Oils  of 

similar  viscosities  (i.e.  Bearing  Oils  Nos.  4,  5  and  6).>  2,3  or  4  |  2,3  or  4 


Large  Size.  . 


Circulation 
Oil  No.  2  or  3 


GAS  ENGINES 


471 


LUBRICATION  CHART  No.  16 
FOR  VERTICAL  GAS  ENGINES 


Quality  of  gas 


Dry  and 
clean 


Moist  and 
impure 


Kmall  Size. 

Up    to    50    H.P.    per  cylinder,    cylinders   and 

bearings j     2  or  2c  2c 

'large  Size. 
Above  50  H.P.  per  cylinder. 

For   bearings  only,  crank  chamber  separated 
from  cylinders  by  a  distance  piece 

Oil  temperature  above  120°F 3  or  4  3  or  4 

Oil  temperature  below  120°F 2  or  3  2  or  3 

For  cylinders  only,  oil  fed  separately  to  pistons | 

by  a  mechanically  operated  lubricator '     2  or  2c  2c 

For  cylinders  and  bearings,  pistons  lubricated 

from  crank  chamber 3  or  4         3c  or  4c 

For  piston  cooling. 

Cooling   system   separate   from  lubricating 

system Circulation  oil  No.  1 

Ditto,  but  joints  leaking  badly j  Circulation  oil  No.  2. 


CHAPTER  XX VI II 
GASOLENE    ENGINES 

Gasolene  engines  are  now  employed  for  a  great  many  purposes, 
such  as: 

Stationary  Engines 
.   Automobiles 
Motor  boats 
Motor  Cycles 

Aeroplanes  and  Dirigible  Airships 
Agricultural  Tractors 

As  the  design  and  lubrication  of  motor-boat  and  stationary 
engines  are  similar  to  those  of  automobile  engines,  the  lubrication 
of  the  former  is  not  specially  dealt  with. 

Agricultural  tractors  are  mostly  run  on  kerosene,  but  their 
design  and  lubrication  are  usually  more  closely  related  to  gas- 
olene engines  than  to  stationary  kerosene  engines;  for  this  reason 
agricultural  tractors  are  here  only  briefly  mentioned.  The 
following  chapters  therefore  refer  to: 

Automobile  Engines 
Motor  Cycles 
Aero  Engines 
Agricultural  Tractors 

AUTOMOBILE  ENGINES 
Classification. — 

Number  of  Cylinders:  1  to  6,  usually  4. 
Horse  Power  per  cylinder:  2.5  to  15  H.P. 
Speed:  1000  to  3000  R.P.M. 
Cooling:  Nearly  always  water  cooling. 
Piston  Rings:  2,  3  or  4. 
Piston  Diameters:  60  to  150  m.in. 
Piston  Strokes:  60  to  180  m.m. 

Cast  iron:  0.003 "  to  0.008". 


Piston  Skirt  Clearances: 


•  Aluminium    Alloy:     0.008"    to 
1 0.012"     (chiefly    for     aeroplane 
( engines) . 
472 


GASOLENE  ENGINES 


473 


Cylinders.  Practically  all  automobile  engines  are  of  the  4- 
stroke  cycle  type  with  4  or  0  vertical  cylinders,  the  great  majority 
having  4  cylinders.  A  few  low  power  automobile  engines  have 
1  or  2  cylinders,  usually  vertical,  rarely  horizontal.  Six-  and 
8-cylinder  "V"  type  engines  are  coming  into  use  in  a  few  high 
power  cars. 

Cooling. — Automobile  engines  are  practically  always  water 
cooled.  Air  cooled  engines  are  less  frequent  than  formerly  and 
are  not  likely  to  increase  in  numbers  as  water  cooled  engines 
give  greater  security  of  operation  over  long  periods  of  service. 

Piston  Rings. — The  number  of  piston  rings  is  usually  three  or 
four,  more  often  the  former.  In  a  very  few  engines  the  number 


FIG.   187. — Piston  with  oil  scraper  ring. 

has  been  reduced  to  two,  and  there  is  probably  no  question  about 
the  soundness  of  reducing  the  number  of  piston  rings  to  two  or 
three  if  they  are  well  designed  and  pegged.  The  piston  friction 
consumes  more  than  half  the  total  amount  of  friction  so  that  by 
having  fewer  piston  rings  the  piston  friction  is  appreciably 
reduced. 

The  question  of  oil  scraper  rings  has  been  the  subject  of  much 
discussion.  Fig.  187  illustrates  a  type  of  piston  with  oil  scraper 
by  which  excess  oil  is  scraped  off  the  cylinder  walls  and  drained 
back  to  the  inside  of  the  piston  through  small  holes. 

Piston  rings  should  preferably  be  pegged,  as  unpegged  piston 
rings  may  rotate  in  use  and  often  get  into  line,  which  allows 
the  oil  to  pass  freely  to  the  top  of  the  piston.  When  piston  rings 


474  PRACTICE  OF  LUBRICATION 

are  allowed  to  rotate  and  remain  round  while  the  cylinders  become 
slightly  oval,  it  is  difficult  for  the  rings  to  maintain  a  complete 
seal,  as  the  oil  film  is  too  thick  at  certain  points  and  therefore 
unable  at  those  points  to  keep  compression  or  explosion  tight. 
This  applies  particularly  to  engines  that  have  been  in  use  for 
some  time  and  have  become  worn.  A  good  method  of  pegging  is 
shown  in  Illustration  Fig.  188.  This  method  prevents  unscrew- 
ing of  the  peg  and  does  not  weaken  the  ring.  In  the  early  days 
piston  rings  were  nearly  always  pegged  as  the  desirability  of 
pegging  was  realized,  but  unfortunately  many  pegs  came  un- 
done and  caused  great  damage  to  pistons  and  cylinders.  The 
peg  illustrated  has  however  given  complete  satisfaction. 

Pistons. — The  piston  is  receiving  heat  all  over  the  top  at  a 
very  high  rate.  This  heat  must  find  its  way  through  the  piston 
barrel  into  the  cylinder  walls  until  it  finalty  reaches  the  cooling 
water  or  is  radiated  into  the  atmosphere.  The  heat  travels 
from  the  centre  of  the  piston  outwards.  Dr.  Charles  E.  Lucke 
therefore  proposes  a  larger  thickness  of  the  piston  head  at  its 


FIG.   188. — Pegged  piston  rings. 

circumference.  When  the  heat  gets  to  the  edge  of  the  piston  it 
must  flow  down  the  piston  barrel,  and  the  thickness  of  the  barrel 
below  the  top  piston  ring  should  decrease  regularly  towards  the 
open  end  of  the  skirt. 

The  piston  expands  irregularly  under  heat,  principally  due  to 
the  gudgeon  pin  bosses.  Even  if  the  piston  and  cylinder  have 
been  turned  and  ground  quite  true,  they  cease  to  be  round  when 
they  become  warm.  These  deformations  are  not  very  consid- 
erable in  the  case  of  cast  iron  cylinders  and  pistons,  but  with 
aluminium  alloy  pistons  this  point  is  particularly  important  as 
the  coefficient  of  expansion  of  aluminium  is  twice  as  great  as  for 
cast  iron.  Several  French  builders  have  overcome  the  deforma- 
Ition  difficulty  by  so  shaping  the  piston  that  when  hot  its  shape 
coincides  with  that  of  the  cylinder.  Aluminium  pistons  conduct 
the  heat  away  much  more  rapidly  than  cast  iron  pistons,  the 


GASOLENE  ENGINES  475 

heat  conductivity  of  aluminium  being  about  15  times  greater. 
Aluminium  pistons  therefore  keep  much  cooler  and  higher 
compressions  can  be  employed  without  " pinking." 

Carbon  deposits  do  not  readily  collect  on  aluminium  pistons 
and  preignition  is  therefore  less  likely  to  occur.  The  advocates 
of  aluminium  alloy  pistons  claim  that  their  use  will  increase 
acceleration,  horse  power,  flexibility,  maximum  speed,  and 
mileage  per  gallon  of  gasolene,  and  at  the  same  time  decrease 
vibration  and  carbon  deposit,  both  in  the  combustion  chamber 
and  in  the  crank  case. 

METHODS  OF  LUBRICATION 

The  parts  requiring  lubrication  are  the  main  shaft  bearings, 
the  crank  pin  bearings,  wrist  pin  bearings,  cam  shaft  bearings, 
timing  gears,  cams,  cam  lifter  guides,  and  cylinder  walls.  Lubri- 
cating systems  may  be  classified  under  five  headings  : 

1.  Full  Force  Feed. — Oil  is  fed  under  pressure  to  the  main 
bearings,  a  portion  of  the  oil  continuing  its  way  to  the  crank  pins 
through  drilled  holes  in  the  crank  shaft,  reaching  finally  the 
wrist  pins  through  either  the  hollow  connecting  rods  or  the  oil 
pipes  attached  thereto. 

The  oil  splashed  away  from  the  crank  pins  and  wrist  pins 
lubricates  the  cylinder  walls  and  finally  returns  to  the  oil  reservoir, 
being  circulated  afresh  by  the  oil  pump. 

2.  Force  Feed. — This  system  is  the  same  as  the  full  force  feed 
system  with  this  exception,  that  the  wrist  pins  are  not  supplied 
with  oil  under  pressure  but  are  lubricated  entirely  by  oil  spray. 

3.  Force  Feed  and  Splash. — Oil  is  forced  to  the  main  bearings 
and  crank  pins  as  with  the  force  feed  system,  but  in  addition 
the  connecting  rods  dip  into  the  oil  collected  in  the  bottom  of  the 
crank  case  or  in  troughs  below  the  crank  pins,  a  constant  level 
being  preferably  maintained  in  the  crank  case  or  in  the  troughs; 
the  oil  overflows  to  the  oil  reservoir  below,  whence  the  oil  is 
circulated   afresh.     By  this  system   the  oil  thrown  from   the 
connecting  rods  is,  therefore,  not  only  the  oil  leaving  the  crank 
pins,  but  also  the  oil  splashed  from  the  dippers  to  all  parts  of  the 
engine. 

4.  Semi-Force  Feed  and  Splash. — Oil  is  supplied  at  low  pres- 
sure to  a  sight  feed  arrangement  on  the  dash  board,  flowing 
from  this  point  by  gravity  to  the  main  bearings,  or  it  may  go 
direct  to  the  main  bearings,  while  a  pressure  indicator  (see  Fig. 
189)  on  the  dash'shows  that  the  oil  is  being  circulated.     The  oil 
leaving  the  main  bearings  collects  in  the  bottom  of  the  crank 


476 


PRACTICE  OF  LUBRICATION 


case  or  in  troughs  below  the  crank  pins;  the  connecting  rods 
dip  into  the  oil  and  splash  it  to  all  parts.  Th  eoil  overflows  from 
the  troughs  or  crank  case  into  the  oil  reservoir  below,  whence 
the  oil  is  circulated  afresh. 

5.  Splash  System. — Oil  is  supplied  to  the  crank  case;  the  con- 
necting rods  dip  into  the  oil  and  splash  it  to  all  parts. 

Pressure  Oiling  Systems. — Supplying  oil  by  the  full  force  feed 
system  to  the  wrist  pins  has  now  been  practically  abandoned, 
except  for  racing  cars,  as  the  difficulty  in  ordinary  automobile 
engines  is  not  that  of  getting  oil  to  the  wrist  pins  but  of  prevent- 
ing too  much  oil  from  splashing  on  to  the  cylinder  walls.  With 
a  high  oil  pressure  the  large  amount  of  oil  leaving  the  wrist  pins 


FIG.   189. — Oil  pressure  indicator. 

tends  to  overlubricate  the  cylinders.  In  fact,  with  most  pressure 
oiling  systems,  splash  guards  fitted  above  the  main  bearings,  as 
illustrated,  Fig.  190,  will  often  prove  advantageous,  reducing 
the  oil  consumption  to  1000  miles  per  gallon  or  better,  whereas 
the  average  oil  consumption  of  motor  car  engines  is  nearer  500 
miles  per  gallon. 

The  splash  guard  must  be  fitted,  as  low  as  possible  over  the 
crank  pin  path,  as  otherwise  the  disturbance  in  the  crank  chamber, 
created  by  the  piston  expelling  and  drawing  in  the  air  through 
the  slits,  causes  excessive  oil  spray  and  increases  the  oil  con- 
sumption instead  of  reducing  it. 

An  oil  relief  valve  should  always  be  fitted  in  connection  with 
pressure  oiling  systems.  The  relief  valve  should  be  so  arranged 


GASOLENE  ENGINES 


477 


as  to. measure  the  pressure  at  a  point  near  the  bearings,  and  the 
oil  pipes  and  drillings  should  be  large  so  that  there  will  always  be 
a  good  pressure  in  the  crank  shaft  and  no  danger  of  the  oil 
channels  choking  up. 

A  pressure  gauge  should  be  arranged  to  indicate  that  the  oil  is 
circulating  under  pressure;  it  is  not  necessary  to  give  the  actual 
oil  pressure.  An  arrangement  like  the  one  shown  in  Fig.  189 


FIG.   190.— Splash  guard. 

is -all  that  is  required  and  may  be  preferable,  because  with  ordi- 
nary pressure  gauges  having  a  scale  indicating  from  0  to  25  or 
50  pounds  it  is  difficult  to  read  the  pressure  when  it  is  only  a 
couple  of  pounds;  and  if  a  low  reading  pressure  gauge  is  used, 
the  pointer,  when  the  car  is  started  on  a  cold  morning,  will  be 
forced  against  the  extreme  end  of  the  scale,  and  is  frequently 
bent  owing  to  the  very  high  oil  pressure  created  by  the  cold 
thick  oil. 

Racing  car  engines  are  frequently  supplied  with  oil  direct  to  the 
piston  in  addition  to  the  oil  spray  from  the  crank  case.  Experi- 
ence proves  the  necessity  of  this,  the  spray  from  the  crank  chamber 
under  high  speed  conditions  not  being  adequate  for  the  cylinder 
lubrication. 


478  PRACTICE  OF  LUBRICATION 

One  weak  point  in  a  pressure  system  is  that  if  the  brasses  are 
worn  or  a  slack  fit  the  oil  escapes  freely,  to  the  detriment  of  the 
other  bearings.  On  occasions  oil  pumps  have  been  found  to 
wear  and  being  worn  they  have  not  been  able  to  pump  sufficient 
oil  to  keep  up  the  oil  pressure,  with  the  result  that  lubrication 
has  failed.  For  these  reasons  some  builders  prefer  the  semi- 
force  feed  and  splash  system,  which  saves  drilling  the  crank  shaft. 

Briefly,  the  essential  problem  of  lubrication  is  to  supply  the 
maximum  quantity  of  oil  to  the  bearings  without  throwing  too 
much  on  to  the  cylinder  walls.  Most  pressure  oiling  systems 
fulfil  the  first  of  these  requirements,  and  if  the  oil  pressure  is 
reasonably  low,  and  if  suitable  splashguards  are  fitted,  or  the 
piston  rings  are  pegged,  the  cylinder  lubrication  will  not  be 
excessive. 

With  the  pressure  oiling  systems,  main  bearings  and  crankpin 
bearings  have  worked  for  long  periods  without  any  wear  at  all, 
a  result  which  can  never  be  obtained  with  splash  lubrication. 
With  splash  lubrication  a  slight  alteration  in  the  oil  level  means 
either  over-lubrication  or  under-lubrication.  The  margin  of 
safety  is  undoubtedly  greater  with  pressure  oiling  systems. 

Splash  Oiling  Systems. — The  oil  spray  is  produced  by  dippers 
fitted  to  the  big  ends.  These  dippers  should  be  only  He  mcn 
wide  and  say  3^  inch  deep,  and  when  cutting  through  the  surface 
of  the  oil  they  should  only  dip  to  a  depth  of  ^{Q  to  J£  inch.  If 
the  dippers  are  wider  or  dip  more  into  the  oil  the  excessive 
oil  spray  thus  formed  means  unnecessary  waste  and  carbon 
deposit. 

In  the  early  days  the  dippers  were  made  in  the  form  of  a  tube 
with  the  point  bent  forward,  it  being  thought  that  the  oil  would 
find  its  way  in  through  the  tube  and  into  the  crank  pin  bearings. 
A  moment's  consideration  will,  however,  show  that  the  centri- 
fugal force  will  at  all  times  be  sufficiently  strong  to  throw  out  any 
oil  that  might  be  present  in  the  oil  tube.  The  effect  of  the  dipper 
is  merely  to  spray  and  splash  oil  to  all  parts  of  the  engine,  and 
the  entrance  of  the  oil  to  the  crank  pins  should  be  made  from 
above,  the  oil  collecting  on  the  lower  end  of  the  connecting  rod 
being  guided  into  the  oil  hole  or  holes  and  thus  reaching  the 
crank  pin  bearings. 

With  the  splash  lubricating  system  and  when  going  up  or 
down  hills,  the  rear  cylinders  get  too  much  oil  and  the  front 
cylinders  get  starved  or  vice  versa.  This  is  the  reason  why  the 
separate  trough  system  was  designed  and  numerous  other 
arrangements  by  which  the  oil  pump  or  the  flywheel  distributes 
the  oil  to  separate  chambers  below  each  crank  pin,  in  order  to 


GASOLENE  ENGINES  479 

ensure  satisfactory  distribution  of  the  oil  also  when  the  car 
is  not  on  the  level. 

As  regards  keeping  up  the  supply  of  oil  in  the  splash  system, 
the  simplest  arrangement  is  to  have  an  oil  container  on  the  dash 
board.  Frequently,  this  container  is  on  the  chassis  level  or 
attached  to  the  crank  chamber.  Either  the  exhaust  pressure  or 
a  pump  may  be  used  to  force  the  oil  to  the  bearings  or  to  the 
crank  chamber,  feeding  so  many  drops  per  minute.  Most  of 
these  arrangements  offer  plenty  of  scope  for  forgetfulness  or  for 
failure  of  the  oil  feed. 

The  trough  system  is  really  a  splash  system  in  which  the  oil 
level  can  be  maintained  at  the  proper  height.  This  system  has 
met  with  wide  favor.  The  amount  of  splash  varies  consider- 
ably with  the  speed  of  the  engine.  Some  builders  have  arranged 
adjustable  troughs,  which  are  raised  or  lowered  simultaneously 
with  the  opening  or  closing  of  the  throttle,  this  being,  however, 
considered  by  many  an  unnecessary  refinement. 

The  semi-force  feed  and  splash  system  is  reliable  and  can  be 
designed  not  to  cause  over-lubrication  of  the  cylinders,  but  it 
has  the  disadvantage  that  the  oil  is  picked  up  from  an  open  trough 
in  which  dirt  can  collect. 

CARBON  DEPOSITS 

Carbon  deposits  may  develop  on  the  piston  heads,  between  and 
behind  the  piston  rings,  on  the  valves  and  sparking  plugs,  and 
inside  the  piston  hollows.  Carbon  deposit  on  the  piston  heads 
may  cause  pre-ignition  and  "pinking"  (which  means  detonations 
caused  by  excessive  compression,  due  to  carbon  reducing  the 
clearance  space).  Deposit  behind  the  rings  may  make  the  rings 
inflexible  in  their  grooves,  preventing  them  from  functioning 
properly;  the  result  is  "blow  past"  the  piston,  excessive  friction 
and  wear,  and  frequently  piston  seizure.  Excessive  deposit  on 
the  valve  seats  prevents  them  from  seating  properly,  causing 
loss  of  power. 

Carbonized  oil  inside  the  piston  hollow  bakes  into  a  crust 
which  in  time  cracks  and  falls  into  the  crank  chamber  contami- 
nating the  oil,  often  with  disastrous  results.  Carbon  deposits 
may  be  due  to  several  causes,  such  as  incomplete  combustion, 
road  dust,  over-lubrication,  too  thin  piston  heads,  etc. 

Incomplete  combustion  is  frequently  caused  by  a  badly  ad- 
justed carburettor  delivering  an  incorrect  mixture  of  the  vapor- 
ized fuel  and  air.  Faulty  timing  of  valves,  possibly  brought 
about  by  wear  and  unsuitable  fuel,  will  also  bring  about  incom- 


480  PRACTICE  OF  LUBRICATION 

plete  combustion,  likewise  a  choked  muffler  or  silencer;  another 
cause  is  defective  or  incorrectly  timed  ignition. 

Road  Dirt  or  Dust. — Road  dirt  or  dust  is  drawn  into  the  cylin- 
ders with  the  intake  air  and  forms  a  base  to  which  any  excess 
oil  will  readily  adhere.  The  soot  resulting  from  imperfect 
combustion  will  likewise  form  a  base  for  the  building  up  of  car- 
bon deposit.  Eventually,  the  deposit  if  not  removed  will  increase 
to  such  an  extent  that  it  becomes  incandescent,  causing  pre- 
ignition,  and  resulting  in  heavy  knocking  of  the  engine. 

Over -lubrication. — The  excess  oil  always  chars  and  causes  a 
certain  amount  of  carbon  deposit.  Excess  oil  may  be  caused  by 
ill-fitting  piston  rings  or  worn  cylinders,  by  too  high  oil  pressure 
or  too  high  oil  level  (splash  oiling  system). 

The  oil  pressure  in  pressure  oiling  systems  is  nearly  always  too 
high.  In  order  to  supply  a  reasonable  flow  of  oil  to  the  last  point 
in  the  oiling  system,  only  two  or  three  pounds'  oil  pressure  is 
usually  required.  Any  excess  pressure  simply  mea'ns  that  too 
much  oil  spray  is  formed  inside  the  engine  from  the  oil  leaving 
the  bearings  and  this  excessive  oil  spray  finds  its  way  out  of  the 
engine  through  the  air  vent  or  elsewhere  and  causes  a  very  excess- 
ive consumption  of  oil.  Another  portion  of  the  excess  oil 
spray  leaks  past  the  pistons  to  the  piston  tops  and  helps  to  in- 
crease the  formation  of  carbon  deposit. 

Over-lubrication  of  the  piston  is  very  general  in  connection 
with  the  splash  system  of  lubrication  owing  to  the  oil  level 
varying  and  usually  being  too  high,  or  owing  to  the  dippers 
dipping  too  deeply  into  the  oil. 

Whereas  a  black  exhaust  indicates  incomplete  combustion,  a 
blue  exhaust  indicates  burning  of  excess  oil  inside  the  combustion 
chamber.  When  the  engine  is  working  with  the  throttle  almost 
closed  as  in  coasting  or  when  the  car  is  standing  with  the  engine 
running  (Doctors'  cars),  the  vacuum  formed  in  the  cylinder, 
particularly  in  high  compression  engines,  sucks  the  oil  past  the 
pistons  into  the  combustion  chamber.  When  the  car  comes 
under  normal  load  again  the  accumulated  oil  is  burned,  giving  a 
blue  smoke  in  the  exhaust,  and  the  result  is  the  formation  of 
carbon  deposits. 

When  the  piston  rings  are  worn  they  should  be  renewed 
and  whether  the  cylinders  are  worn  or  not,  pegging  of  the  piston 
rings  will  always  help  to  overcome  carbon  trouble  by  maintaining 
a  perfect  piston  seal. 

Carbon  deposits  may  be  formed  inside  the  hollow  of  the  piston 
caused  by  too  thin  a  piston  head.  Heat  entering  the  centre  of 
the  piston  cannot  get  away  quickly  enough  when  the  piston  head 


(JASOLENE  ENGINES  481 

is  thin.  The  result  is  that  the  piston  gets  overheated  and  the 
oil  splashed  up  into  the  piston  from  the  crank  chamber  burns 
and  chars.  For  ordinary  automobile  engines  the  thickness  of  the 
piston  head  (cast-iron)  must  not  be  less  than  ^  inch. 

TRANSMISSION 

The  transmission  consists  of  dutch,  gear  box,  and  rear  axle. 
Clutch. — The  clutch  :s  located  between  the  engine  and  the 
gear  box  and  there  are  two  main  types  of  clutches,  viz.: 

(a)  Metal  to  metal  clutches. 

(b)  Leather  or  fibre-faced  clutches. 

The  latter  require  no  lubrication  of  the  contact  surfaces,  but 
the  leather  requires  dressing  with  neatsfoot  oil  or  castor  oil  at 
intervals  to  preserve  it,  say,  every  500  miles.  Metal  to  metal 
clutches  must  be  lubricated  in  order  to  prevent  wear  of  the 
metal  surfaces  and  insure  easy  operation. 

Experiments  have  been  carried  out  with  multiple  disc  clutches 
showing  that  without  lubrication  the  friction  losses  and  the  rise 
in  temperature  are  quite  small,  but  oil  is  required  to  prevent 
rusting  and  abrasion  of  the  plates  and  to  make  the  plates  engage 
without  gripping  fiercely.  A  very  thin  lubricating  oil  is  required 
with  a  view  to  minimizing  the  friction  losses.  At  the  same  time 
the  oil  must  have  sufficient  oiliness  to  prevent  abrasion  of  the 
metal  surfaces,  and  sufficient  viscosity  to  act  as  a  cushion  when 
the  discs  or  plates  are  forced  into  contact. 

If  the  oil  is  too  heavy  in  viscosity  it  becomes  difficult  to  dis- 
engage the  plates  and  it  may  not  be  possible  to  uncouple  the 
engine  quickly  enough.  This  difficulty  is  experienced  with  such 
cars  as  the  Ford,  where  the  engine  oil  is  also  used  for  lubricating 
the  clutch  and  particularly  in  cold  weather  when  the  oil  becomes 
more  viscous.  If  an  oil  too  light  in  viscosity  is  used,  excessive 
wear  takes  place  and  the  plates  grip  too  fiercely. 

With  insufficient  oil  in  the  clutch  over-heating  and  wear  take 
place,  but  the  oil  level  must  be  kept  below  the  clutch  spring. 

With  a  view  to  preventing  abrasion  of  the  plates  an  admix- 
ture of  fixed  oil  is  desirable.  A  very  suitable  mixture  is  one 
containing,  say,  10  per  cent,  to  20  per  cent,  of  sperm  oil  with  a 
viscosity  not  exceeding  120"  Saybolt  at  104°F.  A  mixture  of  the 
engine  oil  with,  say,  50  per  cent,  of  kerosene  is  often  used  with 
good  results. 

Gear  Box. — The  gears  are  best  lubricated  by  means  of  oil 
which  should  be  filled  into  the  gear  box  to  the  proper  level.  If 

31 


482 


PRACTICE  OF  LUBRICATION 


the  oil  level  is  loo  high  the  oil  runs  out  of  the  gear  sliaJ'l  bearftlgs. 
If  the  oil  level  is  too  low  the  gears  do  not  dip  sufficiently  to  splash 
the  oil  to  all  parts  requiring  lubrication. 

The  gears  are  a  source  of  great  loss  of  power.  Experiments 
carried  out  by  the  National  Physical  Laboratory  showed  that 
when  the  gear  box  of  a  32  H.P.  Leyland  gear  box  was  filled  with 
thin  oil  to  a  depth  of  J£,  J-^,  %,  1,  the  efficiencies  of  the  power 
transmission  were  97.5,  94,  90  and  74  per  cent. ;  thus  the  efficiency 
is  appreciably  reduced  when  the  box  is  more  than  a  quarter  full. 
These  experiments  were  made  on  the  top  gear,  but  corresponding 
results  were  obtained  on  the  second  and  third  gears.  Other 
oils  were  tried,  showing  that  the  losses  increased  in  direct  ratio 
to  the  viscosity  of  the  gear  oil. 

Makers  are  beginning  to  realize  the  importance  of  keeping  a 
proper  oil  level;  and  instead  of  the  oil  being  filled  in  from  the  top 
when  it  is  practically  impossible  to  judge  whether  the  correct  oil 


FIG.   191. — Oil  filling  arrangement  for  gear  case. 

level  has  been  obtained,  the  arrangement  illustrated  in  Fig.  191, 
with  a  filling  plug  from  the  side,  is  being  adopted  by  a  number  of 
builders. 

A  refinement  recently  introduced  is  to  have  a  trough  below 
each  gear  wheel,  into  which  they  dip.  The  gear  oil  is  circulated 
by  a  pump  to  keep  the  troughs  filled  with  oil.  It  has  also  been 
proposed  to  squirt  the  oil  into  the  mesh  of  the  teeth.  Both  with 
this  system  and  with  the  one  just  mentioned  thick  gear  oil 
cannot  be  used,  as  it  cannot  be  pumped.  The  gear  box  must 
therefore  be  so  constructed  that  a  low  viscosity  gear  oil  can  be 
employed  without  excessive  loss  of  oil. 

It  is  obviously  desirable  to  use  as  low  a  vicosity  oil  as  possible, 
and  the  only  reason  why  the  engine  oil  is  not  used  in  the  gear  box 
is  because  the  gear  box  is  not  sufficiently  tight  to  permit  the  use 
of  such  an  oil,  so  that  in  order  to  prevent  excessive  leakage  a 


GASOLENE  ENGINES  483 

heavy  viscosity  oil  is  used  or ,  even  a  semi-solid  lubricant,  so- 
called  transmission  greases. 

Transmission  grease  may  be  more  economical  than  oil  but  has 
the  disadvantage  of  causing  greater  loss  in  power  and  it  does  not 
distribute  itself  effectively  to  all  bearings,  so  that  trouble  is 
often  experienced,  particularly  when  there  are  ball  bearings  in 
more  or  less  inaccessible  positions. 

Greases  which  are  too  stiff  or  made  from  unsuitable  materials 
harden  in  use  and  cause  excessive  heating.  The  oil  melts  out; 
the  revolving  gears  cut  tracks  in  the  grease  and  leave  the  gears 
without  any  lubrication  whatsoever. 

When  the  gears  are  inclined  to  engage  noisily,  a  heavier  vis- 
cosity oil  must  be  used,  or  even  a  transmission  grease.  The 
transmission  grease  should  be  of  soft  consistency,  known  in  the 
trade  as  No.  2  Consistency,  or  even  softer,  and  should  preferably 
be  strained  during  manufacture.  The  lime  cup  grease  variety 
is  less  inclined  to  cake  and  harden  than  the  solidified  oils,  so- 
called  soda  greases. 

Rear  Axle. — The  remarks  made  as  regards  the  oil  level  in 
gear  boxes  also  apply  to  rear  axle  casings,  and  it  is  desirable  to 
fit  a  filling  plug  similar  to  the  one  shown  in  Fig.  191. 

The  oil  level  must  not  rise  as  high  as  the  axle  housing,  as, 
notwithstanding  the  packings  provided,  the  oil  will  find  its  way 
along  the  housing,  pass  through  the  outer  bearings  to  the  brake 
drums,  and  cause  the  brakes  to  slip.  Oily  brake  drums  are  sure 
evidence  of  excess  oil  in  the  rear  axle  casing. 

When  the  packings  and  bearings  are  worn,  a  transmission 
grease  or  a  mixture  of  grease  and  heavy  gear  oil  must  be  used 
to  prevent  leakage,  but  ordinarily  a  heavy  viscosity  gear  oil 
should  be  preferred. 

In  case  of  the  worm  wheel  drive,  the  pressure  between  the 
worm  and  the  worm  wheel  is  very  great  and  only  oils  having 
great  oiliness  will  prevent  wear  and  give  satisfactory  results. 
For  this  reason  several  builders  are  recommending  castor  oil  for 
the  worm  wheel  casing. 

Experiments  prove  that  all  heavy  viscosity  fixed  oils  give 
better  results  for  the  worm  lubrication  than  any  type  mineral 
oil,  but  the  heavy  viscosity  filtered  cylinder  oils  come  very  near 
in  lubricating  qualities  to  the  fixed  oils,  and  being  much  lower 
in  price  are  almost  universally  used,  preferably  compounded  with 
from  5  per  cent,  to  10  per  cent,  of  fixed  oil. 

An  interesting  type  of  worm  gear  is  the  one  designed  by  Mr. 
F.  W.  Lanchester  which  is  of  the  hollow  worm  type,  as  distinct 
from  the  parallel  typo.  The  advantage  of  the  hollow  type  is  flint 


484  PRACTICE  OF  LUBRICATION 

the  oil  is  continuously  drawn  in  between  those  parts  where  it  is 
wanted,  so  that  extreme  pressures  can  be  carried  without  trouble. 
This  also  explains  why  at  higher  speeds  the  efficiency  of  the 
Lanchester  gear  is  increased,  because  the  higher  speed  helps  the 
oil  to  wedge  itself  in  between  the  surfaces. 

The  grease  used  for  wheel  bearings  and  other  parts  should  also 
be  of  a  No.  2  Consistency,  in  order  to  distribute  itself  all  over  the 
ball  or  roller  bearing  surfaces.  Most  oil  firms  to-day  sell  a  No. 
3  Consistency,  which  has  been  the  cause  of  innumerable  failures 
of  bearings,  through  failing  to  reach  all  parts,  with  the  result 
that  rusting  and  corrosion  have  set  in,  and  the  bearings  have 
been  ruined.  The  grease  must  comply  with  the  requirements 
for  a  ball-bearing  grease  as  outlined,  page  190.  The  grease  used 
for  the  water  pump  bearings  should  be  a  high  melting  point 
grease  of,  say,  No.  4  Consistency. 

Chain  Drive. — Where  a  chain  drive  is  employed,  the  chains, 
being  exposed,  get  quickly  covered  with  dirt  and  dust.  They 
should  be  oiled  daily  with  the  engine  oil  (gear  oil  does  not  pene- 
trate to  the  link  bearings),  but  it  is  important  to  clean  the  chains 
frequently  (say  every  1000  miles)  by  soaking  them  in  kerosene 
and  afterwards  immerse  them  in  a  bath  of  molten  graphite  and 
tallow.  By  this  treatment  the  chain  will  get  thoroughly  soaked 
with  lubricant  and  wear  will  be  minimized. 

Lubrication  of  Other  Parts. — The  lubrication  of  parts  of  the 
cars  other  than  the  engine,  transmission,  and  rear  axle  is,  as  a  rule, 
much  neglected,  and  for  this  reason  all  parts  should  be  designed 
with  a  view  to  maintaining  good  lubrication,  even  if  the  parts 
do  not  get  the  very  best  attention. 

Shackle  pins,  for  example,  are  now  made  much  larger  than  in 
earlier  days  and  instead  of  being  lubricated  by  grease  they  are 
frequently  designed  with  oil  lubrication.  A  neat  method  is  to 
place  a  small  ball  valve  in  each  pin  which,  when  oiling,  is  pressed 
from  its  seating  by  the  spout  of  the  oil  can. 

MOTOR  CYCLE  ENGINES 

Classification. — The  vast  majority  of  motor  cycle  engines  are 
vertical,  air-cooled,  single-cylinder  engines,  operating  on  the  four- 
stroke  cycle  principle.  Other  types  have  two  cylinders,  either 
placed  horizontally — opposed  type — or  at  an  angle — "V"  type. 
Two-stroke  cycle  engines  are  coming  into  use  as  vertical  one- 
cylinder  engines,  usually  of  small  power. 

Horse  Powers  range  from  1J^  to  8  H.P. 

Speeds  range  from  2,000  to  5,000  R.P.M. 


GASOLENE  ENGINES 


485 


Piston  Rings. — Pistons  in  four-stroke  cycle-engines  usually 
have  three  piston  rings.  Pistons  in  two-stroke  cycle  engines 
usually  have  only  two  piston  rings,  but  these  are  nearly  always 
pegged. 

Piston  Diameter,  Stroke  and  Clearance. — Piston  diameters 
range  from  60  mm.  to  80  mm.  Piston  stroke  ranges  from  60  mm. 
to  100  mm.  Piston  clearances  range  from  0.002"  to  0.005", 
usually  0.003"  to  0.004." 

Compression. — 50  to  80  Ibs.  per  square  inch. 

Bearings. — Roller  bearings  with  short  rollers  are  frequently 
used  for  the  connecting  rods  and  main  bearings  in  order  to  reduce 
friction  and  lubrication  difficulties. 

Lubricating  Systems. 

(a)  Hand  Pump. 

(6)  Semi-automatic  Drop  Feed. 

(c)  Mechanically-operated  Pump. 

(d)  Oil-gasolene  System. 

(a)  Hand  Pump. — The  principle  of  "little  and  often"  should 
never  be  forgotten  where  the  oil  is  fed 

to  the  engine  crank  case  by  hand  pump. 
It  is  better  to  give  half  a  charge  every 
50  miles  than  one  charge  every  100 
miles.  Where  the  oil  is  introduced  at 
great  intervals  it  means  over-lubrica- 
tion after  giving  the  charge,  possibly 
followed  by  under-lubrication  later  on. 
Care  must  be  taken  when  raising  the 
pump  plunger  to  make  sure  that  the 
pump  barrel  fills  with  oil.  When  the 
oil  is  cold  and  thick  it  is  not  uncom- 
mon to  have  considerable  engine 
trouble,  simply  because  the  oil  never 
enters  the  hand-operated  pump,  and 
because  the  rider  has  no  means  of  as- 
certaining whether  the  oil  is  being 
pumped.  For  this  reason  even  hand 
pumps  should  preferably  be  fitted  with 
some  means  in  the  way  of  sight  feeds 
which  indicate  to  the  rider  whether  the 
oil  is  being  pumped  or  not. 

(b)  Semi-automatic  Drop  Feed. — -Several  sight  feed  lubricators 
have  been  designed  to  give  a  more  or  less  continuous  feed  of  oil, 
one  of  the  best  being  illustrated  in  Fig.  192.     The  plunger  (1)  is 


FIG.   192.— Sight  feed  lubri- 
cator for  motor  cycle. 


486  PRACTICE  OF  LUBRICATION 

depressed  and  the  pump  barrel  (2)  fills  with  oil  from  the  supply 
tank.  The  spring  (3)  will  then  endeavor  to  force  the  piston 
upwards,  discharging  the  oil  through  the  sight  feed  (4)  from 
which  the  oil  is  delivered  to  the  engine.  The  oil  is  delivered 
under  a  pressure  of  a  few  pounds  per  square  inch,  and  may  there- 
fore be  delivered  either  to  the  crank  case  itself  or  to  the  piston 
main  bearings,  etc.,  as  required. 

By  this  lubricator  a  fairly  regular  feed  of  oil  can  be  maintained, 
but  of  course  the  feed  will  vary  with  the  temperature  and  the 
viscosity  of  the  oil,  and  is  easily  interfered  with  if  dirt  gets  in 
between  the  adjusting  needle  and  its  seat.  As,  however,  the 
rider  can  always  watch  the  sight  feed,  any  difficulty  in  this 
direction  is  quickly  discovered  and  easily  remedied. 

(c)  Mechanically  Operated  Pump. — There  is  a  distinct  tendency 
towards  the  more  general  use  of  this  system,  which  consists  of 
a  plunger  pump,  preferably  with  adjustible  pump  stroke  and 
operated  by  means  of  gearing  from  the  engine. 

It  is  very  desirable  that  the  speed  of  the  plunger  be  as  low  as 
possible,  as  otherwise  a  low  oil  feed  cannot  be  maintained  with 
certainty,  because  of  the  exceedingly  short  stroke  of  the  plunger. 

The  mechanically  operated  pump  should  preferably  be  pro- 
vided with  a  sight  feed  arrangement  in  order  that  the  driver  may 
know  whether  the  pump  parts  are  in  working  order  and  the  oil  is 
discharged  regularly  to  the  engine. 

(d)  Oil-gasolene  System. — In  this  system  the  oil  is  mixed  with 
the  gasolene  in  proportions  ranging  from  1  part  of  oil  to  from 
4  to  10  parts  of  gasolene  and  the  lubrication  of  the  engine  is 
therefore  not  dependent  on  the  skill  of  the  rider. 

There  are,  however,  many  disadvantages  to  this  system.  If 
too  much  oil  is  used,  excessive  carbonization  takes  place  and  if 
an  attempt  is  made  to  reduce  the  proportion  of  oil  it  is  frequently 
found  that  the  engine  is  poorly  lubricated,  particularly  when  the 
engine  has  been  in  use  for  some  time  and  has  become  slightly 
worn.  The  engine  runs  with  a  harsh  noise  indicating  that  the 
running  parts  are  not  properly  lubricated. 

Oil  has  also  a  tendency  to  combine  with  the  road  dust  which  is 
always  drawn  in  with  the  air  through  the  carburetor,  the  effect 
of  this  being  to  clog  the  working  parts,  particularly  the  needle. 

Points  of  Delivery. — The  simplest  method  of  lubrication  is  to 
deliver  the  oil  straight  to  the  crank-case,  so  that  the  fly  wheel 
dips  into  the  oil  and  distributes  it  to  all  parts  by  creating  an  oil 
fog  in  the  crank  case.  This  is  the  method  practically  always 
used  in  connection  with  hand  pump  lubrication.  Many  manu- 
facturers provide  ducts  cast  in  the  crank-ease  which  collect  the 


GASOLENE  ENGINES  487 

nil  spr.MY  formed  l>v  I  lie  fly  wheel  MIM!  distribute  it  to  the  main 
bearings,  etc. 

In  modern  motor  cycles  the  development  is,  however,  in  the 
direction  of  feeding  the  oil  first  of  all  to  the  main  bearings  and 
sometimes  also  to  the  piston,  the  oil  escaping  from  the  main 
bearings  being  caught  by  a  rim  on  the  fly  wheel  and  by  centrifugal 
action  carried  into  the  big  end.  Feeding  oil  direct  to  the  piston 
appears  only  to  be  necessary  in  high  power  engines  and  for  racing 
purposes.  Lubrication  of  the  gudgeon  pin  is  usually  well  taken 
care  of  by  the  oil  fog  alone. 

In  most  systems  the  oil,  having  done  its  work,  collects  in  the 
sump  at  the  bottom  of  the  crank-case,  is  drawn  off  at  intervals 
and  not  used  over  again.  In  some  systems,  however,  the  oil  is 
circulated  over  and  over  again  through  the  main  bearings,  the 
oil  feed  being  very  slow,  and  done  by  means  of  a  mechanically- 
operated  pump. 

Carbon  Deposit. — In  case  of  over-lubrication,  excessive  car- 
bonizaton  takes  place  on  the  top  and  in  the  hollow  of  the  piston. 
In  order  to  prevent  the  formation  of  carbon  deposit  inside  the 
piston,  some  motor  cycles  are  made  with  a  distance  plate  over  the 
gudgeon  pin,  which  never  attains  a  temperature  high  enough  to 
carbonize  the  oil  splashed  up  from  the  crank-case.  This  arrange- 
ment also  keeps  the  crank  case  and  the  working  parts  enclosed 
therein  much  cooler. 

In  order  to  keep  the  piston  rings  compression  tight,  all  two- 
stroke  engines  should  have  their  rings  pegged,  so  that  the  rings 
will  wear  to  a  fit  with  the  cylinder.  If  they  are  not  pegged  they 
are  inclined  to  move  in  their  grooves  until  the  gaps  get  into  line, 
resulting  in  bad  compression,  excessive  carbonization  of  the  oil, 
an  overheated  crank  case,  and  heavy  wear.  The  method  of 
pegging  the  rings  should  of  course  be  such  that  under  no  circum- 
stances can  the  pegs  unscrew  and  damage  the  cylinder.  (See 
page  474.)  It  is  the  excess  oil  that  causes  carbon  deposit,  and  to 
which  impurities  arising  from  bad  carbonization,  bad  combustion 
or  road  dust,  will  adhere. 

Oil  Consumption. — The  oil  consumption  for  motor  cycle  en- 
gines ranges  from  1000  to  4000  miles  per  gallon  of  oil,  the  average 
being  2500  miles  per  gallon. 

Oil. — It  is  very  important  that  the  oil  should  have  a  sufficiently 
low  setting  point  (say  20°F.  to  25°F.)  so  as  to  flow  freely  during 
the  winter  season;  poor  cold  test  oils  may  not  reach  the  working 
parts  and  the  engines  are  difficult  to  start  when  cold. 

Motor  cycles  usually  do  not  get  too  good  attention,  being 
often  in  the  hands  of  men  who  have  had  little  or  no  technical 


488  PRACTICE  OF  LUBRICATION 

training.  As  a  result  plenty  of  oil  is  the  "cure  all"  employed  for 
most  troubles.  Such  overfeeding  with  oil  means  that  a  great 
deal  of  the  excess  oil  is  burnt  inside  the  cylinder  and  oil  manu- 
facturers should  therefore  aim  at  producing  an  oil  with  a  par- 
ticularly low  tendency  to  carbonize.  That  can  be  accomplished 
by  using  pale,  non-paraffinic  base  oils,  compounded  with  say 
10  per  cent,  of  good  quality  fixed  oil. 

A  low  contents  of  free  fatty  acid  is  desirable  from  the  point  of 
view  of  bearing  lubrication.  A  high  percentage  of  free  fatty 
acid  does  not  seriously  affect  the  cylinder  lubrication,  although 
when  the  engine  is  put  aside  for  some  weeks,  the  result  is  usually 
to  be  seen  in  heavy  rusting  of  the  piston,  rings,  and  cylinder  due 
to  the  acid.  The  real  trouble  caused  by  free  fatty  acid  is,  how- 
ever, corrosion  and  pitting  of  the  balls  or  rollers  in  the  bearings. 
For  this  reason  only  fixed  oils  having  a  low  percentage  of  free 
fatty  acid — say  below  5  per  cent. — should  be  used. 

Semi-drying  oils  like  rape  oil,  cottonseed  oil,  whale  oil,  etc., 
should  not  be  employed  on  account  of  their  gumming  tendency, 
as  the  choking  of  oil  grooves,  etc.,  may  easily  cause  a  lot  of 
trouble. 

The  following  tests  are  characteristic  of  good  motor  cycle 
oils  which  will  suit  practically  all  motor  cycles. 

Specific  gravity * 900-.925. 

f  20°F.-25°F.  for  winter  use. 
Setting  point j  30°F.-40°F.  for  summer  use. 

Open  flash  point 400°F.-420°F. 

Fire  point 440°F.-465°F. 

Saybolt  Viscosity  at  104°F 600"-750". 

Saybolt  Viscosity  at  140°F 240"-300". 

Saybolt  Viscosity  at  210°F.  .  . 70"-80". 

Compound 10  per  cent,  good  quality  fixed  oil. 

AERO  ENGINES  FOR  AEROPLANES,  AIRSHIPS,  ETC. 

The  three  main  types  of  aero  engines  are:- 

Rotary  Engines,  with  revolving  cylinders,  air  cooled. 

Radial  Engines,  with  cylinders  radially  arranged,  either  air 
or  water  cooled. 

"V"  Type  Engines,  with  inclined  double  row  of  cylinders, 
mostly  water  cooled. 

Rotary  Engines. — The  rotary  type  aero  .engine,  as  for  example 
the  Gnome,  presented  from  the  beginning  a  great  many  lubricat- 
ing problems.  In  the  early  types  the  inlet  valve  for  the  petrol- 
air  mixture  was  in  the  centre  of  the  piston  and  this  valve  got 
easily  choked  with  deposit.  In  a  later  type,  the  Monosoupape 


CASOLENE  ENGIKES 


489 


type  (single  valve  type),  one  valve  placed  in  the  top  of  the  cylin- 
der serves  as  both  exhaust  and  inlet  valve,  thus  doing  away  with 
the  inlet  valve  troubles  of  the  earlier  type. 

Only  one  piston  ring  is  used,  made  from  sheet  brass  or  phos- 
phor bronze  and  of  "L"  shape  as  illustrated  in  Fig.  193.  On  the 
compression  and  the  explosion  stroke  the  ring  is  expanded  by  the 
pressure  in  the  cylinder  and  at  the  same  time  is  forced  down  on 
its  seating  in  the  piston  ring  groove,  which  also  holds  a  light 
piston  ring  of  the  ordinary  type  in  order  to  keep  the  expanding 
piston  ring  in  position.  This  ring  being  the  only  one  must  be 
an  absolute  fit  in  the  steel  cylinder  and  it  has  a  vertical  straight 
cut  at  the  point  where  its  two  ends  meet.  This  cut  is  the  weak 
part  of  the  ring  and  gets^  eaten  away  by  even  a  slight  trace  of 
fatty  acid  in  the  castor  oil  used  for  lubrication.  As  soon  as  the 


FIG.   193.  —  "  Gnome"  piston  with  single  piston  ring. 


corners  of  the  cut  in  the  brass  ring  get  rounded,  the  ring  is  no 
longer  able  to  prevent  the  explosion  gases  from  passing  the  piston; 
and  the  cylinder  immediately  becomes  overheated  in  a  straight 
line  following  the  position  of  the  cut  in  the  ring.  The  cylinder 
in  question  will-  be  found  out  of  shape,  being  only  about  Jfe 
inch  in  thickness,  and  must  be  replaced. 

The  gasolene  is  introduced  through  the  hollow  shaft  and  imme- 
diately evaporates  inside  the  crank  chamber.  Gasolene  has  a 
dissolving  effect  on  mineral  lubricating  oil  but  does  not  affect 
castor  oil. 

The  lubricating  oil  is  fed  to  the  oil  pump  through  a  tube  from 
an  elevated  oil  tank.  This  makes  it  necessary  in  cold  weather, 
in  case  the  aeroplane  rises  to  a  considerable  height,  to  use  an 
oil  with  a  good  cold  test,  say  not  above  zero  Fahrenheit.  It 
is  good  practise  to  empty  the  oil  tank  every  night  and  before  a 
new  flight  to  put  the  oil  into  the  tank  hot.  The  tank  should 
preferably  be  placed  so  that  it  may  benefit  to  some  extent  by  the 
heat  from  the  engine  during  flight, 


490  PRACTICE  OF  LUBRICATION 

By  means  of  a  mechanically  operated  plunger  pump  with 
piston  valves  the  oil  is  introduced  through  the  hollow  shaft 
under  a  slight  pressure,  and  the  main  stream  of  oil  divides  itself 
in  seven  different  directions,  i.e.,  for  supplying  oil  to  the  seven 
different  crank  pins,  connecting  rods,  gudgeon  pins,  and  pistons. 
Obviously,  the  oil  holes  all  being  very  tiny,  the  amount  of  resist- 
ance to  the  oil  will  differ,  and  if  there  is  a  slightly  greater  resistance 
in  one  direction  than  in  the  other  six,  this  will  mean  that  in  order 
to  give  sufficient  oil  in  the  one  direction,  the  oil  must  be  fed  very 
copiously.  This  is  one  of  the  reasons  for  the  heavy  oil  consump- 
tion in  this  type  of  motor.  Another  reason  for  a  heavy  oil 
consumption  in  the  " Gnome"  motor  is  the  fact  that  it  is  a  rotary 
engine,  and  the  centrifugal  force  tends  ^o  throw  the  oil  outwards 
and  to  tear  it  away  from  the  cylinder  walls. 

This  means  that  in  order  to  keep  a  sufficiently  thick  oil  film 
on  the  cylinder  walls,  there  must  be  a  constant  spray  of  oil  to 
make  up  for  the  oil  that  is  thrown  out  through  the  cylinders  due 
to  the  centrifugal  force.  As  the  engine  is  air  cooled,  the  top 
portion  of  the  cylinders  gets  very  hot,  in  fact,  the  metal  turns 
blue.  Consequently,  all  the  oil  used  for  lubricating  the  pistons, 
etc.,  is  eventually  burned  in  the  combustion  chambers,  and  if  it 
leaves  deposit,  the  carbon  will  soot  up  the  sparking  plugs  and 
prevent  the  valves  from  seating  properly. 

For  the  old  type  of  Gnome  motor  the  oil  consumption  was 
about  80 grams  per  horse  power  hour.  With  the ' 'Monosoupape" 
engine  the  consumption  has  been  reduced  to  about  25  grams  per 
horse  power  hour.  If  the  oil  consumption  is  reduced  below 
these  figures,  the  margin  of  safety  is  so  low  that  there  is  danger 
of  one  or  several  of  the  pistons  seizing. 

Experience  generally  with  internal  combustion  engines  proves 
that  whenever  the  cylinder  consumption  of  mineral  lubricating 
oil  exceeds  5  grams  per  B.H.P.  per  hour,  excessive  carboniza- 
tion, due  to  burning  of  the  excess  oil,  takes  place.  Mineral 
lubricating  oils  can  therefore  not  be  used  for  lubricating  the 
11  Gnome"  or  any  other  rotary  type  of  aeroplane  engine,  but  this  is 
not  the  only  reason.  Mineral  lubricating  oils  are  deficient  in  oili- 
ness  as  compared  with  fixed  oils.  They  do  not  cling  sufficiently 
to  the  cylinder  walls  to  provide  efficient  lubrication;  they  are 
thrown  out  through  the  the  cylinders  so  quickly  that  the  cylinder 
walls  are  left  dry,  and  if  the  engine  runs  with  such  oils  for  more 
than  a  few  minutes,  the  pistons  seize,  the  cylinders  get  overheated, 
and  the  speed  of  the  engine  falls  below  normal.  If  exceedingly 
viscous  mineral  lubricating  oils  are  used  it  has  been  proved 
possible  to  maintain  the  cylinder  walls  in  a  greasy  condition, 


GASOLENE  ENGINES  491 

but  the  fluid  friction  of  such  oils  is  so  high  that  the  engine  loses 
power  and  the  speed  is  reduced.  Furthermore,  such  oils  produce 
a  very  excessive  amount  of  carbon  deposit  which  is  obviously 
fatal,  and,  finally,  they  have  a  poor  setting  point;  for  this  reason 
alone  they  could  not  be  accepted,  as  aeroplanes  are  exposed  to 
cold  weather  and  the  oil  would  congeal. 

Medicinal  castor  oil,  practically  free  from  fatty  acid,  is  the  only 
oil  which  has  given  satisfactory  results  for  rotary  type  aeroplane 
engines.  It  can  be  used  in  great  excess  without  leaving  any 
carbon  deposit  inside  the  cylinders;  all  the  oil  passing  through 
the  combustion  chambers  burns  away  clean.  Castor  oil  is  only 
slightly  affected  by  the  gasolene,  vapors  in  the  crank  chamber. 
It  has  sufficient  viscosity  to  seal  the  pistons  and  is  possessed  of 
sufficient  oiliness  to  keep  the  cylinder  walls  well  lubricated  in 
spite  of  the  centrifugal  force,  and  it  has  a  viscosity  sufficiently 
low  that  the  speed  of  the  engine  can  be  maintained  at  normal 
for  long  periods.  Castor  oil  has  a  good  cold  test  and  will  not 
congeal  in  cold  weather  or  at  high  altitudes. 

Radial  and  "V"  Type  Engines. — The  great  majority  of  aero 
engines  are  now  of  the  radial  type  or  the  "V"  type.  Although 
these  engines  operate  very  satisfactorily  with  castor  oil  as  a 
lubricant,  yet  there  is  not  the  same  need  for  castor  oil  as  in  the 
case  of  the  rotary  type  engine.  The  oil  is  kept  warm  in  the 
engine  and  circulates  continuously  under  pressure.  The  question 
of  cold  test  is  therefore  not  so  important  and  as  the  centrifugal 
force  does  not  act  here  as  in  the  case  of  the  rotary  type  engines, 
lubricating  oils,  largely  mineral  in  character,  can  nearly  always 
be  employed  with  complete  satisfaction.  It  is  advisable  to  have 
a  certain  percentage,  about  10  per  cent.,  of  good  fixed  oil,  say 
neatsfoot  oil,  mixed  with  the  mineral  oil  in  order  to  minimize  the 
danger  of  seizure  and  to  reduce  friction.  Castor  oil  can  also  be 
used  in  such  mixtures,  but  only  in  the  presence  of  an  animal  oil. 
An  admixture  of  5  per  cent,  castor  oil  and  5  per  cent,  of  lard 
oil  or  neatsfoot  oil  forms  an  excellent  mixture.  If  more  castor 
oil  is  desired,  as  much  as  20  per  cent,  can  be  mixed  with  74  per 
cent,  of  asphaltic  base  mineral  oil  in  the  presence  of  6  per  cent, 
of  lard  oil  By  increasing  the  percentage  of  animal  oil,  even 
greater  proportions  of  castor  oil  may  be  employed. 

Aluminium  pistons  are  particularly  liable  to  cut  and  seize 
during  the  first  five  or  six  hours  testing  owing  to  the  initial 
"growth"  of  the  aluminium.  It  is  particularly  during  this  period 
that  castor  oil  or  oils  containing  a  high  percentage  of  fixed  oil 
show  their  superiority  over  straight  mineral  oils. 

When  aero  engines  with  aluminium  pistons  are  running  at 


492  PRACTICE  OF  LUBRICATION 

maximum  power  the  piston  clearance  is  reduced  to  proper  work- 
ing value,  but  when  the  engines  are  running  at  lower  power  the 
lower  temperature  of  the  piston  brings  about  larger  piston  clear- 
ances, which  explains  why  under  these  conditions  aero  engines 
may  have  a  high  oil  consumption. 

The  consumption  of  lubricating  oil  is  usually  reduced  when 
using  castor  oil  mixtures  in  place  of  pure  mineral  oils.  Some- 
times excessive  oil  consumption  is  caused  by  the  oil  pressure 
being  too  great.  The  following  figures  taken  from  trials  with 
an  8-cylinder  "V"  type  engine  developing  200  H.P.  at  1400 
R.P.M.  clearly  show  the  effect  of  oil  pressure: 

Oil  pressure,  Oil  consumption, 

Ibs.  per  sq.  inch  gallons  per  hour 

70  1.5 

50  0.9 

30  0.5 

Aero  engines  when  used  for  war  purposes  are  examined  and 
cleaned  thoroughly  after  each  trip,  so  that  any  gumminess 
brought  about  by  the  use  of  pure  castor  oil  is  removed.  When 
the  engine  parts  are  not  frequently  cleaned  the  gummy  products 
of  oxidation  soon  become  very  troublesome. 

AGRICULTURAL  TRACTORS 

During  recent  years  agricultural  tractors  have  come  much  into 
prominence  and  their  design  has  largely  been  developed  following 
the  design  of  automobile  engines,  only  experience  has  proved 
that  they  have  to  be  built  more  strongly  to  stand  up  to  the  more 
severe  conditions.  They  are  prone  to  overheating  and  therefore 
must  have  good  radiators  and  fans  in  order  to  keep  the  cooling 
water  from  becoming  too  hot.  In  many  engines  the  cooling- 
water  is  always  boiling  hot.  For  this  reason  very  heavy  vis- 
cosity oils  are  generally  employed,  so  as  to  retain  sufficient  lubri- 
cating power  exposed  to  the  higher  temperatures. 

Kerosene  is  the  fuel  generally  adopted  instead  of  gasolene, 
both  the  fuel  and  the  intake  air  being  preheated  by  the  jacket 
water  and  the  exhaust  heat  respectively,  and  in  some  tractors 
the  air  passes  a  dust  extractor  to  prevent  dust  entering  the 
cylinders. 

Many  different  systems  of  lubrication  are  employed,  ranging 
from  splash  to  force  feed,  as  well  as  intermediate  systems,  and 
in  addition  a  number  of  tractors  have  adopted  mechanically 
operated  lubricators  which  distribute  the  oil  by  means  of  plunger 
pumps  to  the  various  points  requiring  lubrication.  As  the  oil 


GASOLENE  ENGINES  493 

Food  pipes  from  such  lubricators  are  generally  exposed,  low  setting- 
point  oils  are  demanded. 

There  is  a  general  endeavor  to  enclose  the  gear  and  differen- 
tials and  to  lubricate  them  with  oil  in  preference  to  grease. 

There  are  many  different  types  of  agricultural  tractors;  and 
although  their  design  often  approaches  automobile  designs,  a 
great  many  are  adaptations  of  stationary  kerosene  oil  engines. 
The  lubrication  requirements  must  therefore  be  studied  for 
each  particular  type  and  make,  and  the  author  will  not  attempt 
to  give  any  specific  recommendations  in  the  same  way  as  was 
done  with  gas  engines. 

LUBRICATING  OILS  FOR  GASOLENE  ENGINES 

The  oil  must  have  such  a  viscosity  and  setting  point  that  it 
can  be  distributed  with  certainty  to  all  parts  of  the  engine,  even 
in  cold  weather.  Low  setting  point  oils  are  particularly  re- 
quired where  the  feed  pipes  are  exposed  as  is  frequently  the  case 
in  the  " Semi-Force  Feed  and  Splash  System"  of  lubrication. 
A  low  setting  point  is  always  advantageous  in  a  motor  oil, 
particularly  during  cold  weather,  because  of  the  greater  ease 
in  starting  the  engine  from  cold. 

When  the  engine  has  cooled  down  over  night  and  the  oil  has 
become  very  thick  it  may  be  difficult  to  start  the  engine.  This 
is  important  in  connection  with  high  power  engines  which  are  at 
all  times  difficult  to  start  by  hand,  and  even  where  self-starters 
are  fitted  a  low  setting  point  is  always  appreciated,  because  it 
practically  ensures  starting  at  the  first  attempt.  With  a  thick 
sluggish  oil  the  self-starter  has  so  much  work  to  do  that  it  only 
revolves  the  crank  shaft  slowly ;  the  magneto  may  not  give  a  spark 
at  such  a  slow  speed  and  carburation  will  be  too  sluggish  to 
provide  a  satisfactory  explosive  mixture. 

The  temperature  of  the  cylinder  walls  in  water  cooled  engines 
will  not  be  higher  than  250°F.  to  300°F.  This  moderate  tem- 
perature enables  the  lubricating  oil  to  remain  on  the  cylinder 
walls  and  perform  its  function  as  a  lubricant.  The  inner  surface 
of  the  oil  is,  however,  swept  by  the  hot  explosion  gases,  the  maxi- 
mum temperature  of  which  is  about  2500°F.  and  the  inner  part 
of  the  oil  film  is  therefore  continuously  being  burned  away. 
Some  oils  volatilize  without  leaving  residue;  other  oils  decompose 
and  deposit  free  carbon  similar  to  what  happens  when  " cracking" 
oils  during  distillation.  Lubricating  oils  made  from  naphtenic 
and  asphaltic  base  crudes  belong  to  the  first-mentioned  variety 
and  have  therefore  proved  bettor  oils  for  motor  cylinders  than 


494  PRACTICE  OF  LUBRICATION 

paraffin  base  oils,  which  are  more  inclined  to  "crack"  and  form 
carbon. 

Pale,  low  setting  point,  non-paraffinic  base  oils  are  therefore 
the  best  lubricants  when  considering  the  cylinder  requirements 
only.  Air  cooled  cylinders  obviously  require  oils  of  higher 
viscosity  than  water  cooled  cylinders.  As  the  same  oil  is  used 
for  lubricating  cylinders  and  bearings,  the  requirements  of 
both  must  be  taken  into  consideration  when  selecting  a  motor 
oil. 

Bearings  with  small  clearances  are  usually  lubricated  by  a 
pressure  oiling  system,  and  oil  of  practically  any  viscosity  can  be 
used  as  long  as  the  pump  will  circulate  the  oil. 

In  order  to  guard  against  the  oil  pressure  dropping  too  low 
(worn  oil  pump,  worn  bearings,  choked  oil  passages)  medium  or 
heavy  viscosiy  oils  are  nearly  always  used  with  pressure  oiling 
systems.  France  is  the  country  which  has  particularly  favored 
pressure  oiling  systems  and  heavy  viscosity  motor  oils. 

Bearings  which  are  worn  and  have  large  clearances  need  a  heavy 
viscosity  oil  to  prevent  knocking. 

With  the  splash  system  of  lubrication  a  thin  or  medium  viscosity 
oil  must  always  be  used  because  a  heavy  viscosity  oil  cannot  be 
splashed  to  all  parts  with  certainty. 

The  use  of  an  oil  of  the  wrong  viscosity  will  cause  wear,  due 
either  to  the  oil  being  too  light  in  viscosity  or  to  the  fact  that  the 
oil  is  too  viscous  to  be  distributed  with  certainty  under  the  con- 
ditions prevailing  in  the  engine.  Whereas  wear  of  the  crank  pin 
bearings  or  main  bearings  is  indicated  by  a  dull  thumping  noise, 
wear  of  the  wrist  pins  is  indicated  by  a  clear  metallic  knocking. 

Thinning  of  oil  has  been  generally  experienced  during  recent 
years,  due  to  the  use  of  unsuitable  gasolene  substitutes  or  petro- 
eum  spirits  containing  too  high  a  percentage  of  "heavy  end" 
products.  The  less  volatile  products  pass  the  piston  freely  and 
thin  the  oil  in  the  crank  chamber.  The  only  remedy  is  to  use  a 
heavier  viscosity  oil  than  the  one  which  is  known  to  give  satis- 
faction, change  the  oil  in  the  crank  case  more  often,  at  least 
every  2000  miles. 

•  It  is  a  curious  fact  that  the  "heav>  ends"  at  the  same  time  as 
they  cause  thinning  of  the  oil  tend  to  keep  the  pistons  clean  and 
free  from  carbon  deposit.  The  heavy  ends  are  of  a  kerosene 
nature  and  are  present  on  the  piston  in  liquid  form.  Their 
cleansing  action  is  therefore  akin  to  the  effect  of  mixing  kerosene 
with  lubricating  oil  to  give  cleaner  piston  lubrication  in  large  gas 
engines. 

Thinning  of  the  oil  due  to  crank  case  heat  is  experienced  with 


GASOLENE  ENGINES  495 

racing. ear  engines  or  raring  motor  boat  engines,  ami  is  counter- 
acted by  passing  the  oil  through  coolers,  i.e.,  nests  of  tubes  cooled 
by  the  air  rushing  past  or  by  sea  water. 

The  bearing  oil  requirements  call  for  oils  that  retain  their 
viscosity  well  under  heat.  In  this  respect  paraffin  base  oils 
are  better  than  asphaltic  base  oils.  For  this  reason  many  oil 
firms  use  mixtures  of  asphaltic  base  and  paraffin  base  oils  so  as 
to  produce  oils  which  have  reasonably  low  setting  points,  and 
a  fairly  low  tendency  to  carbonize,  and  which  will  not  thin  too 
much  under  heat.  Other  firms  use  straight  paraffin  base  oils 
highly  filtered  to  remove  coloring  matter,  but  such  oil*  have 
high  setting  points  and  produce  carbon  of  a  hard  brittle  nature, 
although  a  lesser  amount  than  dark  colored  oils. 

The  admixture  of  fixed  oil,  preferably  non-drying  oils  like 
lard  oil  or  cocoanut  oil,  improves  the  viscosity  curve  and  reduces 
the  tendency  to  carbonize.  An  admixture  of  from  5  to  10  per 
cent,  of  good  quality  fixed  oil  is  nearly  always  conducive  to  good 
results,  providing  that  the  mineral  oil  is  of  suitable  character. 

For  racing  purposes  castor  oil  is  frequently  used  on  account  of 
its  excellent  viscosity  and  non-carbonizing  quality.  Other  fixed 
oils  are  much  lower  in  viscosity,  in  fact,  too  low  to  give  good 
results  unless  mixed  with  heavy  viscosity  mineral  oils,  but  such 
mixtures  do  not  equal  pure  castor  oil  for  racing  purposes. 

For  everyday. use  in  touring  cars,  etc.,  no  oils  should  be  used 
containing  more  than,  say,  10  per  cent,  of  fixed  oils,  as  in  con- 
tinuous service  all  fixed  oils  produce  gummy  deposits,  which  may 
choke  the  oil  passages  and  bring  about  excessive  heating  of  the 
bearings  or  even  worse  results. 

As  regards  the  tendency  to  carbonize  it  has  been  suggested 
that  a  good  motor  oil  (or  the  mineral  base  of  a  motor  oil)  must 
have  only  a  slight  tendency  to  emulsification  with  water  and 
that  the  percentage  of  the  oil  distilling  over  below  300°C.  under 
vacuum  is  important.  As  regards  emulsification  tendency,  water 
rarely  enters  the  oiling  system  in  an  automobile  engine,  and  if  it 
does  so  accidentally  (leaky  water  jacket),  the  water  will  never  get  a 
chance  to  separate  from  the  oil.  The  oil  pump  draws  from  the 
very  bottom  of  the  reservoir  and  will  certainly  churn  any  water 
effectively  together  with  .the  oil  in  circulation  and  form  an 
emulsion,  no  matter  what  oil  is  used.  But  the  suggestion  is 
based  on  an  element  of  truth,  because  if  the  mineral  oil  emulsifies 
badly  with  water,  it  contains  a  portion  of  unstable  hydrocarbons, 
which  on  decomposing  (coloring  matter  for  example)  may 
produce  carbon.  The  author  feels,  however,  that  too  much 


496  PRACTICE  OF  LUBRICATION 

value  should  not  be  attached  to  the  emulsification  test,  when 
judging  motor  oils. 

As  regards  the  distillation  test  of  motor  oils  under  vacuum  up 
to  300°C.,  the  oil  film  as  a  whole  is  not  exposed  to  such  conditions. 
The  author  thinks  very  little  oil  evaporates  in  the  oil  film,  but 
that  the  inner  portion  of  the  oil  film  is  " cracked,"  the  oil  being 
suddenly  decomposed  or  volatilized.  In  the  distillation  test 
the  nature  of  the  oil  undergoes  no  change  whatever. 

The  carbon  test  suggested  by  Conradson  (see  page  64)  or 
some  test  on  those  lines  is  much  more  likely  to  reproduce  con- 
ditions akin  to  what  takes  place  inside  a  motor  cylinder. 

INFLUENCE   OF   ENGINE   CONSTRUCTION   ON   THE   CHOICE    OF 

MOTOR  OIL 

In  selecting  a  motor  oil  it  is  necessary  to  scrutinize  closely 
the  details  of  construction. 

High  Viscosity  Oil  is  called  for  with  large  diameter  pistons,* 
long  piston  strokes  (tendency  to  piston  " rocking"),  large  piston 
clearances  (aluminium  pistons  in  particular),  few  or  ill-fitting 
piston  rings,  worn  pistons  and  cylinders,  high  compression,  worn 
bearings,  air  cooling  or  poor  water  cooling  (agricultural  tractors, 
for  example)  hot  climatic  conditions,  racing  car  engines,  most 
pressure  oiling  systems,  etc. 

Low  Viscosity  Oil  is  called  for  with  small  diameter  pistons,  short 
piston  strokes,  high  piston  speed,  small  piston  clearances,  normal 
number  of  well  fitting  or  pegged  piston  rings,  low  compression, 
normal  bearing  clearances,  efficient  water  cooling,  cold  climatic 
conditions,  splash  oiling  systems,  etc. 

"Non-Carbonizing"  Oils  (i.e.,  pale  colored,  non-paraffinic  base 
oils  with  or  without  admixture  of  fixed  oil)  are  called  for  where 
the  oil  consumption  is  excessive.  When  the  oil  consumption 
is  maintained  at  1000  miles  per  gallon  or  less  one  need  not  fear 
much  trouble  from  carbonization  of  the  oil. 

Admixture  of  fixed  oil  appears  to  be  necessary  or  at  any  rate 
desirable  with  aluminium  pistons  operating  in  steel  cylinders, 
as  aluminium  does  not  work  well  together  with  steel  and  easily 
" drags"  and  seizes.  Mineral  oil  does  not  give  the  same  margin 
of  safety  when  used  straight,  i.e.,  without  admixture  of  fixed  oil. 

When  the  oil  consumption  is  very  excessive,  as  with  the  rotary 
type  aeroplane  engines,  only  pure  medicinal  castor  can  be  used. 

MOTOR  OILS 

Most  oil  firms  market  several  grades  of  motor  oil  under  pro- 
prietory  names,  and  each  can  or  drum  is  also  marked  with  the 


GASOLENE  ENGINES  497 

consistency  of  the  oil,  such  as  light  body,  medium  body,  etc. 
Opinions  differ  among  oil  firms  as  to  what  constitutes  a  light 
oil,  medium  oil,  and  so  on,  but  the  following  viscosities,  setting 
points  and  colors  may  be  considered  as  representing  the  best 
practice  for  temperate  climates.  In  hot  climates  low  setting 
points  are  not  needed.  Table  No.  28  gives  some  characteristics 
of  typical  motor  oils. 

TABLE  28 

fighT  ^ght      i  Medium     Heavy          *£% 


Saybolt  viscosity  @  104°F  
Setting  point  °F.  ! 

175 

0 

250 

10 

400 
35 

'   650 
40 

1000 
40 

Color,  Lovibond  (Y±  inch  cell)  .  . 

20 

30 

100 

200 

300 

Hough  recommendations  for  the  various  grades  are  given  in  Lubrication 
Chart  No.  17. 


LUBRICATION  CHART  NO.  17 
FOR  GASOLENE  ENGINES 

"Extra  Light"  and  "Light."  For  Ford  cars  and  other  cars, 
chiefly  American  make,  employing  the  splash  system  of  lubrica- 
tion, also  for  many  European  cars  with  small  power,  high  speed 
engines.  The  extra  light  grade  is  usually  too  light  for  European 
cars. 

"Medium."  This  is  the  correct  grade  for  the  vast  majority 
of  cars,  other  than  Ford  cars,  also  for  a  fair  number  of  motor 
trucks. 

"Heavy."  Largely  used  in  Europe  for  motor  trucks  and  for 
Continental  cars,  French  and  Italian  make  in  particular,  em- 
ploying force  feed  lubrication. 

Mixed  with  6  per  cent. -10  per  cent,  of  good  quality  fixed  oil, 
this  oil  will  suit  most  water  cooled  aeroplane  engines  of  the  "V" 
type  or  the  radial  type;  it  will  also  prove  an  excellent  oil  for 
most  motor  cycles. 

"Extra  Heavy."  This  grade  compounded  with  up  to  10  per 
cent,  of  good  quality  fixed  oil  is  recommended  for  "V"  type 
and  radial  type  air  cooled  aeroplane  engines. 

Medicinal  (Pharmaceutical)  Castor.  For  rotary  aeroplane 
engines  exclusively. 

Clutch  Oil. — For  multiple  plate  metal  clutches.  This  oil 
should  have  a  Saybolt  viscosity  at  104°F.  not  exceeding  100", 
and  should  preferably  contain  10  per  cent,  of  non-drying  fixed  oil. 

32 


498  PRACTICE  OF  LUBRICATION 

When  clutch  oil  is  not  available  a  mixture  of  engine  oil  with  at 
least  50  per  cent,  kerosene  may  be  used. 

Gear  Oil. — For  gear  box  and  rear  axle  casing.  A  dark  or 
filtered  cylinder  stock  having  a  rather  high  setting  point  usually 
gives  good  results.  A  high  setting  point  makes  the  oil  thick  at 
ordinary  temperature,  so  that  no  oil  leaks  out  from  the  gear  box, 
but  as  soon  as  the  car  starts  runnng  the  oil  thins,  so  that  the 
friction  losses  in  the  gear  box  are  kept  low.  Some  makers  give 
the  gear  oil  a  high  setting  point  by  mixing  with  it  a  percentage 
of  petroleum  jelly  or  paraffin  wax.  For  worm  gear  back  axle 
drives  the  gear  oil  should  preferably  contain  5  per  cent,  to  10 
per  cent,  of  non-gumming  fixed  oil. 


CHAPTER  XXIX 
KEROSENE  OIL  ENGINES  AND  SEMI-DIESEL  ENGINES 

As  the  hot  bulb  or  vaporizer  is  a  characteristic  feature  of  prac- 
tically all  of  these  engines,  they  are  frequently  called  hot-bulb 
engines. 

Horizontal  oil  engines  are  used  for  driving  shafting  and  ma- 
chinery in  machine  shops,  woodworking  shops,  dairies,  also  used 
for  driving  refrigerating  plants,  electric  generators,  pumping 
machinery,  agricultural  tractors  and  for  a  variety  of  purposes  in 
"out  of  the  way"  districts.  .*•,.* -., 

Vertical  oil  engines  are  chiefly  used  for  marine  service,  for  fish- 
ing boats  and  pleasure  boats;  they  are  also  used  for  driving  agri- 
cultural tractors  and  for  many  purposes  in  "out  of  the  way" 
districts,  in  the  same  way  as  horizontal  oil  engines. 

Classification. — Oil  engines  may  be  classified  as  shown  in 
Table  No.  29. 

TABLE  No.  29 

1    No.  of    I     H.P.  per       Revolution 
cylinders       cylinder         per  minutes 


i 

Horizontal 

oil 

engines   (pistons  not  water-' 

1  to 

4 

1 

to 

90 

600 

to 

180 

cooled) 

Horizontal 

oil 

engines 

(pistons  water-cooled) 

1  to 

1 

90 

to 

200   180 

to 

120 

Vertical  oil 

engines  .  . 

1  to 

1 

to 

125  :900 

to 

160 

Starting. — When  starting,  the  hot  bulb  is  heated  to  a  dull  red 
color  by  means  of  a  gasolene  or  kerosene  blow  lamp.  Engines 
employing  electric  ignition  are  started  on  gasolene  till  they  get 
warmed  up. 

Small  oil  engines  are  started  by  hand,  large  oil  engines  by  com- 
pressed air.  The  air  used  for  starting  is  compressed  by  a  small 
belt  driven  compressor  operated  by  the  oil  engine  and  the  air  is 
stored  in  reservoirs. 

After  starting,  the  engines  operate  automatically  and  the  blow 
lamp  is  removed,  the  hot  bulb  being  thereafter  kept  hot  by  heat 
from  the  explosions. 

Injecting  the  Fuel. — The  fuel  is  injected  under  great  pressure 
through  a  specially  constructed  spray  nozzle  in  order  to  produce 

499 


500  PRACTICE  OF  LUBRICATION 

a  very  fine  fuel  spray  mid  gel  complete  combustion.  Several 
makers  use  compressed  air  of  250  to  450  Ibs.  pressure  for  injecting 
the  fuel,  which  greatly  assists  in  producing  a  finely  atomized 
fuel  spray  and  in  getting  complete  combustion. 

In  some  small  engines  the  fuel  is  fed  by  gravity  from  a  tank 
into  the  air  inlet  valve  so  arranged  that  every  time  the  air  valve 
opens,  fuel  is  admitted,  atomized  by  the  in-rushing  air  and 
carried  into  the  engine.  Obviously,  only  light  oils  like  kerosene 
can  be  used  in  this  manner. 

In  some  Semi-Diesel  engines  the  piston  head  is  apt  to  get  very 
hot,  and  can  only  be  kept  sufficiently  cool  by  employing  water 
injection.  The  hot  piston  head  heats  the  air  in  the  crank  cham- 
ber and  reduces  the  capacity  of  the  engine;  it  also  means  a  warm 
gudgeon  pin.  For  these  reasons  it  is  good  practice  to  make  the 
piston  in  two  parts,  a  partition  plate  preventing  the  crank  cham- 
ber air  from  coming  into  contact  with  the  piston  head. 

In  vertical  oil  engines  employing  force  feed  circulation,  the  piston 
should  be  at  least  Y±  inch  thick  in  the  centre  to  avoid  overheating 
and  carbonization  of  the  oil  in  the  piston  hollows. 

PRINCIPLE  OF  OPERATION 

Oil  engines  operate  on  the  four-stroke  cycle,  or  the  two-stroke 
cycle  principle,  but  by  two  different  methods,  the  fuel  being 
either  introduced  during  the  suction  stroke  or  at  the  instant  of 
maximum  compression  (Semi-Diesel  principle). 

Four-Stroke  Cycle  Principle  of  Operation.— First  Method 
(Fig.  194).  Practically  exclusively  used  in  low  compression  oil 
engines  (40  to  70  Ibs.  compression)  employing  light  fuels,  chiefly 
kerosene. 

1st  St.oke  (Suction). — Air  is  drawn  in  through  air  inlet  valve  and  at  the 
same  time: 

(1)  fuel  is  admitted  into  the  air  (by  gravity  or  carburetor)  and  atomized  or 

(2)  fuel  is,  by  means  of  the  fuel  pump,  injected  into  the  hot  bulb  and  there 
vaporized.     In  either  case  the  piston  moves  outwards,  the  cylinder  being 
filled  with  a  more  or  less  complete  mixture  of  air  and  fuel  vapor,  consti- 
tuting the  fuel  charge.     Exhaust  valve  is  closed. 

2nd  Stoke  (Compression). — The  piston  moves  inwards,  compressing  the 
fuel  charge  into  the  hot  bulb  to  a  pressure  of  40  to  70  Ibs.  Inlet  valve  and 
exhaust  valve  are  closed. 

3rd  Stroke  (Power). — Firing  of  the  compressed  fuel  charge  by  electric 
ignition  or  spontaneously  by  the  high  temperature  existing  in  the  hot  bulb, 
explosion  and  expansion,  the  piston  being  forced  outwards  during  its  power 
stroke.  Inlet  valve  and  exhaust  valve  are  closed. 

4th  Stroke  (Exhaust). — Piston  moving  inwards,  driving  out  the  burnt 
gases,  through  exhaust  valve.  Inlet  valve  is  closed. 


KEROSENE  OIL  ENGINES  AND  SEMI-DIESEL  ENGINES        501 


A  few  makers  fit  an  extra  valve  called  a  " timing  valve"  in  the 
"neck"  between  the  hot  bulb  and  the  cylinder.     It  is  operated 


First'S.troke  Second  Stroke 

Suction  Compression 

FIG.   194. — Four  stroke  cycle  principle  of  operation,  kerosene  oil  engines. 


Third  Stroke- 
Power 


Fourth  Stroke 
Exhaust 


First  Stroke 
Suction 

FIG.   195.- 


.    Second  Stroke  Third  Stroke 

Compression  Power 

-Four  stroke  cycle  principle  of  operation,  semi-Diesel  engines. 


Fourth  Stroke 
Exhaust 


from  the  cam  shaft  and  opens  communication  between  the  hot 
bulb  and  the  working  cylinder  at  the  moment  it  is  desired 


502 


PRACTICE  OF  LUBRICATION 


thai  the  explosion  shall  take  place.  A  fairly  high  compression 
can  therefore,  be  employed  without  the  danger  of  premature 
explosions. 

Second  Method  (Fig.  195).— Used  in  four-stroke  cycle  semi- 
Diesel  engines  employing  besides  kerosene  also  heavier  fuels, 
such  as  gas  oil  and  black  fuel  oil. 

1st  Stroke  (Suction). — The  piston  moves  outwards,  sucking  in  air  through 
the  air  inlet  valve.  Exhaust  valve  is  closed. 

2nd  Strok^  (Compression). — The  piston  moves  inwards,  compressing  the 
air  into  the  hot  bulb  to  a  pressure  of  150  to  300  Ibs.  Inlet  valve  and  exhaust 
valve  are  closed. 

3rd  St.oke  (Power). — Fuel  oil  is  sprayed  into  the  hot  bulb  (either  solidly 
or  mixed  with  compressed  air) ;  the  fuel  burns  and  the  high  pressure  de- 
veloped forces  the  piston  outwards  during  its  power  stroke.  Inlet  valve 
and  exhaust  valve  are  closed. 


First  Stroke 
Compression 


Second  Stroke 
Power 


FIG.   196. — Two  stroke  cycle  principle  of  operation,  semi- Diesel  engines. 

4th  Stroke  (Exhaust). — The  piston  moves  inwards,  driving  out  the  burnt 
gases  through  exhaust  valve.  Inlet  valve  is  closed. 

As  the  fuel  is  injected  under  pressure  at  the  instant  of  maxi- 
mum compression  (same  as  in  Diesel  engines)  this  method  is 
called  the  "Semi-Diesel"  principle  of  operation.  It  is  called 
"Semi-Diesel"  because  the  compression  (150  to  300  Ibs.)  is  con- 
siderably lower  than  in  Diesel  engines  (500  Ibs.  compression),  so 
that  the  heat  of  compression  must  be  assisted  by  the  heat  from 
the  hot  bulb  in  firing  the  fuel. 

Two -stroke  Cycle  Principle  of  Operation,  as  employed  by 
two-stroke  cycle  semi-Diesel  Engines  (Fig.  196). 


KEROSENE  OIL  ENGINES  AND  SEMI-DIESEL  ENGINES        503 

All  moving  parts  of  the  engine  are  enclosed  in  a  crank  chamber 
fitted  with  large  air  inlet  valves. 

1st  Stroke  (Compression). — The  rising  piston  covers  the  air  port  and  the 
exhaust  port.  The  air  which  has  filled  the  cylinder  is  compressed  to  a 
pressure  from  150  to  300  Ibs.  pressure  per  square  inch. 

This  is  the  compression  stroke. 

During  the  upward  movement  of  the  piston,  air  is  sucked  into  the 
enclosed  crank  chamber  through  the  air  valves. 

2nd  Stroke  (Power). — When  the  piston  is  near  the  top  of  its  stroke,  fuel 
is  injected  through  the  spray  nozzle  into  the  hot  bulb.  The  atomized  fuel 
is  ignited  and  burned  by  the  heated  compressed  air  and  the  hot  bulb,  and 
the  high  pressure  developed  forces  the  piston  downwards.  Shortly  be- 
fore reaching  the  bottom  of  its  stroke  the  piston  uncovers  the  exhaust  port 
through  which  the  burned  gases  escape;  later  the  air  port  is  uncovered,  allow- 
ing compressed  air  from  the  crank  chamber  to  enter  the  cylinder,  driving 
out  the  burned  gases  and  filling  the  cylinder  with  clean  air. 

This  is  the  power  stroke. 

While  the  piston  is  moving  downwards,  it  is  compressing  the  air  in  the 
enclosed  crank  chamber,  the  air  valves  being  closed. 

Thus  the  cycle  consists  of  two  strokes  (one  idle  stroke  followed 
by  one  power  stroke). 

Cooling. — Oil  engines  are  cooled  in  a  similar  manner  to  gas 
engines  except  that  a  number  of  small,  low  compression  oil 
engines,  used  for  agricultural  purposes,  have  no  cooling  water 
circulation.  The  cooling  water  jacket  is  open  at  the  top,  forming 
a  hopper  containing  a  fair  quantity  of  water,  which  during  opera- 
tion of  the  engine  heats  up  and  boils.  Marine  oil  engines,  of 
course,  use  sea  water  for  cooling  purposes. 

Water  Injection. — In  some  engines,  it  is  customary  on  heavy 
loads  to  arrange  for  a  small  amount  of  water  droppng  into  the 
vaporizer  or  into  the  air  inlet  valve  or  passage.  The  water  turns 
into  steam  and  has  a  softening  effect  on  the  character  of  the 
explosions,  resulting  in  smoother  running  of  the  engine.  It  also 
enables  higher  compression  to  be  carried. 

FUEL 

Fuels  used  in  oil  engines  are:  Kerosene,  Gas  Oil  and  Black 
Fuel  Oil  (often  referred  to  as  " Crude  Oil"). 

Kerosene  is  the  fuel  mostly  used  in  low  compression  oil  engines 
and  also  frequently  used  in  semi-Diesel  oil  engines.  It  is  too 
heavy  to  vaporize  properly  in  most  carburettors,  but  will  vaporize 
satisfactorily  in  the  hot  bulb.  If  the  heat  of  the  hot  bulb  is 
much  above  a  faint  red  heat,  the  kerosene  decomposes  and  forms 
soot.  If  the  heat  of  the  hot  bulb  is  much  below  n.  faint  rod  heat, 
the  kerosene  does  not  vaporize  properly. 

Keeping  the  temperature  of  the  hot  bulb  uniform  is  conse- 
quently of  the  greatest  importance.  In  some  oil  engines  an 


504  PRACTICE  OF  LUBRICATION 

adjustable  portion  of  the  exhaust  gases  is  carried  around  the 
vaporizer,  which  makes  its  possible  to  regulate  the  temperature 
of  the  hot  bulb  as  required  to  suit  the  load.  Advancing  or  retard- 
ing the  ignition  according  to  the  load  also  helps  to  regulate  the 
hot  bulb  temperature. 

When  the  work  done  by  the  engine  varies  considerably,  the 
hot  bulb  will  generally  get  too  hot  on  a  heavy  load  and  too  cold 
on  a  light  load. 

Gas  Oil. — Gas  oils  constitute  the  principal  fuels  used  in  semi- 
Diesel  oil  engines.  The  hot  bulb  must  be  slightly  warmer  with 
gas  oils  than  with  kerosene,  as  gas  oils  are  not  so  easily  vaporized. 

Black  Fuel  Oil  is  generally  the  residuum  from  crude  petroleum 
after  all  gasolene  and  kerosene  have  been  distilled  off.  It  may 
also  be  a  mixture  of  heavy  petroleum  residual  oils  and  gas  oil. 
Black  fuel  oils  are  largely  used  in  semi-Diesel  oil  engines. 

Uniform  Fuel. — When  the  engine  has  been  carefully  ad  justed 
to  suit  a  particular  class  of  fuel,  it  is  very  important  that  the 
fuel  supplies  should  be  as  uniform  in  quality  as  possible,  in  order 
to  obtain  highest  efficiency  and  to  obviate  the  necessity  of 
further  adjustment;  otherwise,  incomplete  combustion  will  take 
place  and  will  interfere  with  lubrication. 

METHODS  OF  LUBRICATION 

Horizontal  Oil  Engines  and  Semi-Diesel  Engines  are  lubricated 
exactly  in  the  same  way  as  horizontal  small  or  medium  size  gas 
engines,  the  oil  being  distributed  from  separate  lubricators  or 
from  a  mechanically  operated  lubricator  to  all  points. 

Vertical  Oil  Engines  due  to  the  high  speed  at  which  they  operate, 
have  the  working  parts  enclosed  in  a  crank  chamber,  and  employ 
the  following  methods  of  lubrication : 

(a)  Splash  System  of  Lubrication,  similar  to  vertical  gas 
engines  or  automobile  engines. 

(6)  Force  Feed  Circulation  System,  similar  to  vertical  automo- 
bile engines. 

(c)  Mechanically  Operated  Lubricators. 

Systems  (a)  and  (b)  are  fully  described  under  sutomobile 
engines  and  are  used  only  in  connection  with  low  compression 
four-stroke  cycle  oil  engines. 

As  the  crank  chamber  is  enclosed,  the  heat  radiated  from  the 
pistons  and  cylinder  walls  is,  to  a  large  degree,  retained  in  the 
crank  chamber,  so  ihat  the  oil  in  the  crank  chamber  gets  very 
warm,  the  resulting  temperature  being  from  100°  to  160°F. 
If  a  temperature  of  140°  is  greatly  exceeded,  the  life  of  the  oil 
will  be  reduced,  and  it  may  throw  down  a  dark  deposit. 


KEROSENE  OIL  ENGINES  AND  SEMI-DIESEL  ENGINES        505 


The  oil  in  the  crank  chamber  is  always  more  or  less  affected  by 
the  admixture  of  fuel,  which  has  not  been  properly  vaporized 
(and  burned)  inside  the  working  cylinder,  but  mixes  with  the  oil 
on  the  cylinder  walls  and  gradually  works  down  past  the  piston 
rings  and  drops  into  the  crank  chamber.  The  result  is  that  the 
oil  becomes  thinner  and  its  lubricating  qualities  are  greatly 
affected.  The  oil  becomes  dark  in  color,  due  to  black  residual  or 
carbonized  matters  coming  down 
from  the  pistons,  dropping  into  the 
crank  case  and  mixing  with  the  oil. 

System  (c). — A  mechanically 
operated  force  feed  lubricator  is 
alwaj's  used  in  connection  with  the 
two-stroke  cycle  oil  engines  or  semi- 
Diesel  engines,  whether  vertical  or 
horizontal.  A  splash  or  force  feed 
system  must  not  be  used,  as  the  oil 
spray  would  contaminate  the  air 
which  is  drawn  through  the  crank 
chamber.  The  lubricator  is  ope- 
rated by  the  engine  and  feeds  oil  to 
the  cylinder,  crank  pin  (by  a  banjo 
arrangement),  gudgeon  pin,  and 
sometimes  also  to  the  main  bear- 
ings, which,  however,  are  sometimes 
ring  oiled  and  occasionally  lubricated 
by  grease. 

Piston. — The  oil  is  introduced 
under  pressure  into  the  cylinder, 

usually  at  two  points,  one  at  the  front  and  one  at  the  back,  and 
preferably  timed,  so  that  the  oil  is  injected  between  the  first 
and  second  piston  rings  at  the  exact  moment  when  the  piston  is 
in  its  lowest  position. 

Gudgeon  or  Wrist  Pin. — One  of  the  oil  feeds  from  the  mechani- 
cally operated  force  feed  lubricator  feeds  oil  through  the  cylinder 
wall,  so  timed  as  to  inject  the  oil  into  the  cylinder  to  a  central 
oil  passage  in  the  wrist  pin.  Fig.  197  shows  a  scoop  arrangement 
now  very  generally  employed. 

As  in  two-stroke  cycle  engines  cold  air  is  constantly  drawn 
through  the  crank  case,  this  is  kept  fairly  cool,  but  there  is  always 
the  danger  of  impurities  and  dirt  in  the  air  getting  into  the  work- 
ing surfaces  of  the  various  bearings. 

Main  Bearings. — Where  the  main  bearings  are  lubricated  with 
grease,  there  is  considerable  loss  in  power,  due  to  the  friction,  as 


FIG.   197. — Wrist  pin  lubrication. 


506 


PRACTICE  OF  LUBRICATION 


thr  hearing  temperature  must  rise  l<>  M.  point  where  <ht(. 
melts  before  it  starts  lubricating. 

Leakage  of  air  from  the  crank  chamber  must  be  guarded 
against,  the  troublesome  places  being  the  main  bearings  and  the 
exhaust  port.  Fig.  198  shows  the  most  common  form  for  pre- 
venting leakage  through  the  main  bearings.  It  consists  of  a 
bronze  ring  revolving  with  the  shaft;  it  has  a  very  good  sliding 


FIG.  200. — Preventing  leakage  from  crank  chamber. 

fit  on  the  collar  and  is  pressed  against  a  turned  face  of  the  crank 
case  by  means  of  light  springs. 

Fig.  199  shows  a  simple  type,  consisting  of  a  leather  ring  fitting 
snugly  against  the  shaft  and  revolving  together  with  a  thin  brass 
ring,  say  %  inch  thick,  which  is  forced  against  the  casing  by  the 
leather  and  the  air  pressure.  The  leather  must  be  renewed  at 
intervals,  as  it  perishes  due  to  the  action  of  the  lubricating  oil. 

Fig.  200  shows  a  design  embodying  a  packed  gland. 

Leakage  of  the  rings  is  often  due  to  dirt  in  the  intake  air 


KEROSENE  OIL  ENGINES  AND  SEMI-DIESEL  ENGINES        507 

getting  between  the  faces;  the  grit  may  often  be  " washed"  out 
by  liberal  use  of  an  oil  syringe. 

Some  builders  of  low  power  engines  employ  grease  for  main 
bearing  lubrication,  the  film  thus  provided  being  sufficient  to 
prevent  air  leakage.  The  grease  is  applied  through  Stauffer 
cups  or  spring  grease  cups,  or  preferably  through  compressed 
air  grease  cups  like  the  "Menno."  The  grease  should  be  of  a 
soft  to  medium  consistency,  so  as  not  to  increase  the  friction 
more  than  need  be. 

The  feed  pipes  should  have  no  bends  and  should  be  placed  at  a 
.steep  angle,  say  over  60°,  so  that  if  the  bearings  get  unduly  warm 
some  of  the  grease  in  the  pipes  will  melt  and  run  into  the  bearings 
on  its  own  accord. 

Governor. — Irregular  running  is  sometimes  experienced  with 
engines,  governed  on  the  hit-and-miss  principle.  The  cause  is 
often  that  governor  parts  stick,  due  to  the  use  of  an  unsuitable 
oil.  Occasional  cleaning  with  kerosene  is  therefore  desirable, 
as  many  of  the  best  oil  engine  oils  are  slightly  gumming,  and  it 
is  not  often  practicable  to  use  a  thin  straight  mineral  oil  for  the 
special  benefit  of  the  governor. 

If  the  exhaust  valve  spindle  sticks,  a  liberal  supply  of  lubricat- 
ing oil  will  only  aggravate  the  trouble.  Kerosene  should  be 
applied  and  will  usually  prove  effective. 

DEPOSITS 

Deposits  may  arise  from  one  or  several  of  the  following  causes : 
impurities  in  the  intake  air,  overfeeding  of  oil,  unsuitable  oil, 
impurities  in  the  fuel,  unsuitable  fuel,  hot  bulb  too  hot  or  too 
cold,  improper  fuel  vaporization,  incomplete  combustion,  water 
injection. 

Where  in  low  compression  oil  engines  deposits  have  developed 
inside  the  combustion  chamber,  they  often  (and  particularly  if 
the  water  cooling  is  defective)  become  incandescent  and  cause 
pre-ignitions. 

Impure  Intake  Air. — The  same  remarks  apply  as  for  gas 
engines  (page  455). 

Overfeeding  of  Oil. — Excess  oil  passing  to  the  cylinders  causes 
carbon  deposits  to  develop  behind  and  between  the  piston  rings, 
the  amount  depending  upon  the  quality  of  the  oil. 

Unsuitable  Oil. — Too  low  viscosity  oil  fails  to  provide  satis- 
factory lubrication;  wear  follows,  the  metallic  wearings  baking 
together  with  charred  oil  and  forming  deposits;  an  increased  oil 
feed  will  only  aggravate  the  trouble.  Too  viscous  an  oil  will 
not  spread  properly  and  may  thus  bring  about  similar  results. 


508  PRACTICE  OF  LUBRICATION 

Impurities  in  Heavy  Fuel  Oils. — When  the  fuel  oil  contains 
too  much  free  carbon  and  ash,  the  unburned  impurities  will 
deposit  themselves  on  the  cylinder  walls.  They  will  adhere  to 
the  lubricating  oil  and  form  a  deposit,  causing  heavy  wear  of 
cylinder  walls  and  piston  rings. 

Unsuitable  Fuel. — A  fuel  containing  too  much  asphalt  or 
being  too  thick  to  flow  readily  will  not  be  properly  atomized 
and  does  not  burn  completely  during  combustion.  The  un- 
burned portions  will  accumulate  on  the  piston  top,  behind  and 
between  the  piston  rings,  etc.,  and  form  carbonaceous  deposits. 

Hot-Bulb  Temperatures. — The  hot-bulb  temperature  may 
become  too  high,  usually  owing  to  heavy  engine  loads.  This 
high  temperature  causes  cracking  of  the  oil  particles  when  they 
meet  the  highly  heated  wall  of  the  hot  bulb  and  the  combined 
effect  of  the  high  temperature  and  pressure  prevailing  is  to 
gasify  the  fuel,  and  at  the  same  time  to  decompose  the  fuel 
to  a  great  extent.  The  splitting  up  of  the  heavy  hydro-car- 
bons into  light  hydro-carbons  always  throws  out  a  certain 
amount  of  carbon  in  the  form  of  coke,  which  accumulates  in  the 
hot  bulb  and  when  it  reaches  the  cylinder  interferes  with 
lubrication. 

Too  low  a  temperature  of  the  hot  bulb  is  frequently  experi- 
enced under  light  load  conditions  and  the  result  is  that  when  the 
fuel  particles  reach  the  wall  of  the  hot  bulb  they  become  only 
partially  gasified  and  some  of  the  heaviest  hydro-carbons  in  the 
fuel  leave  a  bituminous  residue  of  a  sticky  nature  which  is  bound 
to  reach  the  piston  and  piston  rings  and  is  very  objectionable. 
When  the  engine  becomes  cold  these  sticky  deposits  solidify  like 
glue  and  many  cases  have  been  known  where  it  has  been  almost 
impossible  to  move  the  piston  once  the  engine  has  cooled  down. 

For  each  class  of  fuel,  whether  kerosene,  gas  oil,  or  black  fuel 
oil,  there  is  a  certain  range  of  hot-bulb  temperature  within  which 
the  fuel  will  be  completely  gasified  without  leaving  any  appreci- 
able residue  in  the  hot  bulb.  It  is  obviously  desirable  that  this 
range  of  temperature  should  be  as  wide  as  possible. 

Improper  fuel  vaporization  is  apt  to  take  place  where  the  fuel 
is  fed  by  gravity  through  the  air  inlet  valve,  as,  due  to  the 
fact  that  the  fuel  is  not  heated,  the  inrushing  air  does  not  afford 
sufficient  means  for  breaking  up  and  atomizing  the  fuel;  the 
results  are  similar  to  those  under  light  load  conditions  with  the 
vaporizer  too  cold. 

Incomplete  combustion  is  chiefly  due  to  bad  atornization,  but 
may  also  be  due  to  the  vaporizer  being  too  cgld,  or  to  faulty 
timing  of  the  valves.  When  the  spray  is  coarse,  due  to  the 


KEROSENE  OIL  ENGINES  AND  SEMI-DIESEL  ENGINES        509 

fuel  being  too  viscous  or  to  the  fuel  valve  being  out  of  order, 
or  to  too  low  fuel  pressure,  etc.,  the  combustion  of  the  fuel  charge 
becomes  incomplete,  i.e.  some  particles  of  the  fuel  are  so  big 
that  they  burn  only  on  their  surfaces — they  are  charred.  The 
result  is  that,  during  the  power  stroke  and  the  exhaust  stroke, 
the  cylinder  is  full  of  dense  black  smoke  (black  exhaust) 
which  blackens  and  contaminates  the  oil  film  on  the  cylinder 
walls. 

A  finely  atomized  spray  is,  therefore,  very  necessary  if  lubri- 
cation troubles  are  to  be  avoided,  and  in  many  engines  unsatis- 
factory atomization  and  incomplete  combustion  are  often 
unavoidable  under  light  load  conditions. 

Water  Injection. — In  some  engines,  particularly  marine  engines, 
it  is  customary  to  arrange  for  a  small  amount  of  water  dropping 
into  the  vaporizer  or  into  the  air  inlet  valve  or  passage.  The 
water  turns  into  steam,  and  has  a  softening  effect  on  the  character 
of  the  explosion,  resulting  in  smoother  running  of  the  engine  on 
heavy  loads.  The  " water  drips"  should  be  used  only  under 
heavy  loads.  If  used  under  light  load  conditions,  or  if  used 
in  excess,  the  water  will  not  evaporate  completely;  it  will  tend 
to  wash  away  the  oil  film  and  destroy  lubrication,  resulting  in 
heavy  wear  and  carbonaceous  deposits.  In  enclosed  engines 
oiled  by  the^splash  or  force  feed  circulation  system,  excess  water 
will  reach  the  crank  chamber  and,  mixing  with  the  oil,  cause 
trouble  through  emulsification. 

The  water,  unless  it  is  distilled  water,  contains  a  certain 
amount  of  salts  which  are  deposited  inside  the  engine  when  the 
water  evaporates  and  act  like  grit  between  the  piston  rings  and 
cylinder  walls. 

SELECTION  OF  OIL 

In  order  to  select  the  correct  oil  for  an  oil  engine,  it  is  necessary 
to  consider  the  piston  clearance,  the  piston  rings  (their  number 
and  whether  they  are  pegged  or  no) ,  the  temperature  of  the  water 
jacket,  the  method  of  lubrication,  whether  the  combustion  is 
clean  or  otherwise,  etc.,  etc.  A  few  of  these  points  are  considered 
in  the  following. 

Piston  and  Piston  Rings. — By  far  the  largest  amount  of  friction 
is  between  the  piston,  piston  rings  and  cylinder  walls.  Nothing 
is  therefore  so  important  as  the  satisfactory  and  efficient  lubrica- 
tion of  the  piston. 

It  is  important  that  the  piston  clearance  should  not  be  excess- 
ive. In  some  of  the  early  types  of  semi-Diesel  engines  the 
piston  clearance  is  large  and  tends  to  bring  about  "piston  rocking/' 


510  PRACTICE  OF  LUBRICATION 

necessitating  the  use  of  exceedingly  viscous  lubricating  oils  to 
prevent  the  explosion  gases  from  blowing  past  the  piston. 

Some  semi-Diesel  engine  manufacturers  are  still  recommending 
oils  as  viscous  as  steam  cylinder  oils  for  piston  lubrication, 
and  the  result,  as  might  be  anticipated,  is  that  besides  an  excess- 
ive amount  of  power  consumed  by  piston  friction  there  is 
excessive  wear  of  the  piston  rings  and  cylinder  walls.  Such 
viscous  oils  aggravate  troubles  with  deposits  from  whatever 
source  they  may  arise. 

If  friction  is  to  be  reduced  to  a  minimum  the  piston  clearance 
must  only  be  sufficient  to  allow  easy  sliding  motion  of  the  piston 
under  conditions  of  heavy  load,  and  the  piston  rings  should  be 
slightly  softer  than  the  liner  and  pegged,  so  that  they  will  wear 
to  a  fit  with  the  shape  of  the  cylinder. 

This  " pegging"  of  the  rings  is  most  essential.  Each  piston 
ring  should  be  numbered  and  always  put  back  in  the  same  groove 
after  examination.  If  piston  rings  are  not  pegged  they  move  in 
their  grooves  and  the  gaps  may  easily  work  into  line,  with  the 
result  that  the  explosion  gases  blow  past  the  piston,  charring 
the  lubricating  oil  and  causing  excessive  wear. 

The  piston  rings  should  be  a  good  fit  in  their  grooves ;  they  act 
like  valves,  being  bright  on  their  bottom  surface  and  dull  on 
their  top  surface.  If  the  outer  surface  of  the  rings  in  contact 
with  the  cylinder  wall  is  dull,  the  dullness  indicates  leakage  past 
the  ring  during  operation.  If  piston  clearances  are  normal  and 
piston  rings  of  the  right  material  and  pegged,  it  is  possible  to 
use  medium  viscosity  lubricating  oils,  and  the  piston  friction  will 
be  found  to  be  very  reasonable.  Where  the  piston  rings  are  not 
" pegged,"  a  very  heavy-bodied  oil  is  occasionally  used,  in  order 
to  seal  the  piston  and  prevent  too  much  oil  from  passing  the 
piston  rings. 

Combustion. — When  clean  combustion  is  maintained,  straight 
mineral  oils  often  give  satisfactory  results.  But  when  carbon 
deposit  is  formed  inside  the  engine,  due  to  the  hot  bulb  tempera- 
ture being  too  high  or  too  low,  or  due  to  incomplete  atomization 
of  the  fuel  or  to  unsuitable  fuel,  etc.,  such  deposits  will  ordinarily 
accumulate  and  clog  the  piston  rings,  making  them  inflexible  in 
their  grooves,  with  the  result  that  they  no  longer  keep  compres- 
sion or  explosion  tight,  and  heavy  friction  and  wear  immediately 
follow. 

Experience  has,  however,  proved  that  even  extreme  cases  of 
carbonization  of  the  nature  just  referred  to  have  been  cured  by 
using  castor  oil,  rape  oil,  olive  oil,  lard  oil,  or  mixtures  of  such 
oils  with  mineral  oil  in  various  proportions. 


KEROSENE  OIL  ENGINES  AND  SEMI-DIESEL  ENGINES        511 

All  fixed  oils,  i.e.  vegetable  oils  and  animal  oils,  contain  a  fair 
proportion  of  oxygen  and  in  all  probability  this  oxygen  during 
the  explosion  period  assists  in  burning  away  the  carbonaceous 
deposit. 

The  effect  of  the  compound  is  to  prevent  deposits  from  baking 
together  and  forming  a  crust.  The  little  globules  of  compound 
mixed  with  the  mineral  oil  burn  away  clean  and  continuously 
break  up  the  deposits,  so  that  they  may  be  swept  out  with  the 
exhaust  or  work  their  way  past  the  piston  to  the  outside. 

We  know  that  many  vegetable  oils  are  much  more  inclined  to 
produce  gumminess  exposed  to  the  air  than  animal  oils,  so  that 
animal  oils  should  generally  be  preferred  for  mixing  with  mineral 
oil,  the  percentage  of  animal  oil  required  being  entirely  dependent 
on  the  degree  of  carbonization  taking  place  inside  the  engine. 

Speaking  generally,  an  admixture  of  from  6  per  cent,  to  15  per 
cent,  of  lard  oil  to  a  mineral  oil  of  suitable  characteristics  will  give 
clean  lubrication  in  all  normal  cases. 

Water  Injection. — Many  marine  semi-Diesel  engines  are  in 
the  hands  of  fishermen  and  others  who  are  not  particularly 
conversant  with  the  working  of  the  engines,  with  the  result  that 
the  engines  get  scant  attention  generally.  As  regards  the  water 
injection  it  is  generally  kept  on  whether  the  engine  is  on  a  heavy 
or  a  light  load.  The  result  is  that  the  internal  lubrication 
becomes  very  poor  unless  compounded  lubricating  oils  are  used. 
Pure  mineral  oils  are  simply  washed  away  from  the  piston, 
rusting  of  parts  and  heavy  friction  and  wear  being  the  unavoid- 
able result.  The  excess  water  also  contaminates  the  bearing 
oil,  but  when  the  bearing  oil  is  compounded  it  emulsifies  with 
the  water  and  the  bearings  may  be  quite  satisfactorily  lubricated, 
the  only  drawback  being  that  the  emulsified  oil  collecting  in  the 
base  of  the  engine  cannot  be  filtered  and  used  afresh. 

For  oil  engines  in  which  the  combustion  is  not  clean,  or  where 
water  injection  is  employed,  compounded  oils  are  therefore  essen- 
tial to  satisfactory  lubrication,  while  for  oil  engines  with  clean 
combustion  and  without  water  injection,  straight  mineral  oils 
may  be  used. 

For  obvious  reasons,  compounded  oils  are  not  so  satisfactory 
as  straight  mineral  oils  in  force  feed  circulation  oiling  systems; 
if  a  compounded  oil  is  needed  because  of  the  cylinder  require- 
ments, a  non-drying  fixed  oil  should  be  used  for  compounding 
and  as  small  a  percentage  as  possible. 

Oil  Consumption. — Oil  engines  are  frequently  extravagantly 
lubricated,  either  because  of  the  lubricators,  or  because  it  is  not 
possible  to  give  the  engines  the  necessary  doge  attention,  Ex- 


512  PRACTICE  OF  LUBRICATION 

cessive  oil  consumption  means,  however,  not  only  waste  of  oil 
but  also  increased  tendency  to  form  carbon  deposit,  so  that  oils 
having  " non-carbonizing7'  properties  will  be  given  a  decided 
preference  in  most  cases  where  overfeeding  takes  place. 

These  remarks  apply  particularly  to  marine  oil  engines  and 
Semi-Diesel  land  engines. 

Whereas  the  consumption  of  oil  in  horizontal  oil  engines  is 
very  similar  to  the  oil  consumption  of  small  and  medium  size 
horizontal  gas  engines  (page  466)  the  consumption  of  other  oil 
engines  may  be  anything  from  50  per  cent,  to  100  per  cent,  higher, 
depending  upon  circumstances. 

For  lubrication  of  oil  engines,  oils  similar  in  viscosity  and 
general  characteristics  to  gas  engine  oils  Nos.  2c,  3c,  and  4c  are 
required. 

The  oils  should  be  compounded  with  6  per  cent,  to  15  per  cent,  of 
non-drying  fixed  oil  unless  for  special  reasons,  such  as  having  to 
use  the  oil  engine  oil  also  on  other  machinery  for  which  a  com- 
pounded oil  is  considered  unsatisfactory,  it  is  preferred  to  use 
the  oil  without  the  admixture  of  fixed  oil. 

Some  white  bearing  metals,  rich  in  lead,  are  quickly  attacked 
by  free  fatty  acid  in  the  oil,  and  may  for  this  reason  demand  the 
use  of  a  straight  mineral  oil. 

In  the  Lubrication  Chart  for  oil  engines  and  semi-Diesel 
engines  given  below,  gas  engine  oils  Nos.  2c,  3c  and  4c  are  recom- 
mended, but  a  note  is  made  as  to  the  percentage  of  fixed  oil 
required  which,  speaking  generally,  is  greater  than  for  gas  engine 
oils  proper,  but  otherwise  characteristics  are  similar. 


KEROSENE  OIL  ENGINES  AND  SEMI-DIESEL  ENGINES        513 


LUBRICATION  CHART  No.  18 
FOK  KEKOSENE  OIL  ENGINES  AND  SEMI-DIESEL  ENGINES 


Horse  power 
per  cylinder 


n        .„„:„„  nii 


Per  cent,  of  eom- 
pound  required 


Low  Compression  Oil  Engines: 

(a)  Open  types,1  nearly  always 
horizontal Up  to  50 

(b)  Enclosed  types,  nearly  al- 
ways vertical Above  50 

Employing    splash    oiling 

system 

Employing  force  feed  oil- 
ing system. 

1  Semi- Diesel  Engines,  Whether 

Vertical  or  Horizontal Up  to  50 

Above  50 


No.  2c  Up  to  15 

No.  3c  Up  to  15 

No.  2c  or  No.  3c|  Less  than  10 

. 

No.  3c  or  No.  4ej  Less  than  10 


No.  3c 


No.  4c 


I  Usually   less 

than  10 
Usually      less 

than  10 


1  In  such  rare  cases,  where  very  excessive  carbonization  and  gumming  takes 
place,  the  engine  is  either  badly  designed  or  adjusted,  or  out  of  order,  or  the 
operating  conditions  are  very  exceptional  (long  periods  of  light  load  opera- 
tion, for  example).  Under  such  conditions  pure  castor,  lard,  rape,  olive, 
etc.,  may  be  used  temporarily  and  will  give  clean  or  comparatively  clean 
lubrication,  but  such  oils  are  expensive  and  usually  have  other  drawbacks, 
causing  gumming  or  corrosion. 


CHAPTER  XXX 

DIESEL  ENGINES,  LAND  AND  MARINE 
LAND  DIESEL  ENGINES 

Classification. — Practically  all  land  Diesel  engines  are  of 
vertical  construction;  only  a  few,  notably  in  Germany,  are  of 
horizontal  construction.  Land  Diesel  engines  may  be  classified 
as  shown  in  Table  No.  30. 

TABLE  No.  30 

No.   of  cylinders  H.P.    per   cylinder       II. P.M. 


Four- stroke  cycle  engines •        1  to  4 


10  to  300 


(Practically  all  land  Diesel  engines;    are  of  this  ty 
Two-stroke  cycle  engines 4  to  6  200  to  650 


450  to  150 

pe.) 

150  to  100 


Land  Diesel  engines  below  100  H.P.  are  used  for  various  pur- 
poses, but  from  100  H.P.  to  4,000  H.P.  they  are  principally  used 
for  driving  electric  generators  in  electrical  power  stations  or  in 
large  works  or  mills. 

MARINE  DIESEL  ENGINES 

Classification. — All  marine  Diesel  engines  are  vertical  and  can 
be  classified  as  shown  in  Table  No.  31. 

TABLE  No.  31 

No.   of  cylinders; H.P.    per    cylinder       R.P.M. 


Four-stroke  cycle  engines 

Slow  speed 2  to  8  50  to  350       300   to    90 

(Practically  all  main  engines  in  motor  s  hips  are  of  this  type.) 
High  speed 2  to  12  12  to  350       600  to  300 

(Practically  all  auxiliary  engines  in  motor  ships  and  all  main  engines  in 
submarines  are  of  this  type.) 

Two-stroke  cycle 

engines 2  to  6          12  to  650  450  to  90 

(Very  few  main  engines  in  motor  ships  are  of  this  type.  Small  auxiliary 
engines  in  motor  ships  are  occasionally  of  this  type.  Main  engines  in  sub- 
marines are  seldom  of  this  type.) 

514 


DIESEL  ENGINES,  LAND  AND  MARINE  515 

Slow  Speed  Marine  Diesel  Engines  are  used  as  main  engines  in 
the  merchant  marine  service  for  ship  propulsion  and  are  usually 
reversible.  A  few  ships  have  been  built  with  non-reversible 
Diesel  engines,  either  driving  electric  generators  which  produce 
current  for  operating  slow  speed  electric  motors  driving  the 
propeller  direct,  or  driving  centrifugal  pumps  supplying  water 
under  pressure  to  "Foettinger"  transformers,  which  can  be 
made  to  rotate  in  either  direction  and  at  variable  speeds,  driving 
the  propellers  direct. 

The  auxiliary  machinery,  such  as  pumps,  winches,  steering 
gear,  etc.,  on  board  a  Diesel  motor  ship  is  operated  either  electri- 
cally, by  steam,  hydraulically,  or  by  compressed  air. 

High  Speed  Marine  Diesel  Engines  are  used  as  main  engines  in 
torpedo  boats,  submarines,  small  coasters,  yachts,  launches,  etc., 
and  in  other  cases  as  auxiliary  engines  (electric  generator  engines 
for  example)  where  limited  weight  and  space  are  of  primary 
consideration. 

SPECIAL  TYPE  DIESEL  ENGINES 

Double- Acting  Diesel  Engines. — A  great  deal  of  experimental 
work  is  being  done  to  develop  the  double-acting  Diesel  engine 
employing  either  the  four-stroke  cycle  or  the  two-stroke  cycle 
principle.  Their  construction  is  very  similar  to  that  of  large 
gas  engines.  There  are  only  a  few  double-acting  land  Diesel 
engines  in  operation  and  they  are  of  horizontal  construction. 

The  Junker  Diesel  Engine,  often  called  the  double-piston  erv- 
gine,  is  a  special  type  embodying  the  two-stroke  cycle  principle, 
with  two  opposed  pistons  in  each  cylinder. 

Solid  Injection  Diesel  Engines  dispense  with  the  air  compressor 
and  inject  the  fuel  under  an  enormous  pressure  (4000  Ibs.  per 
square  inch) ,  atomizing  it  mechanically.  These  engines  (Vicker's 
type)  are  largely  used  for  submarines. 

CONSTRUCTIONAL  POINTS 

The  main  engines  aboard  a  Diesel  ship  are  always  of  the  cross- 
head  type,  with  the  external  parts  partly  or  entirely  enclosed. 

With  trunk  piston  engines,  wear  of  the  thrust  collars  on  the 
propeller  shaft  would  cause  trouble  with  pistons,  but  does  not 
affect  the  flat  crosshead  guides  in  crosshead  type  engines.  Quite 
apart  from  this  consideration,  there  is  a  growing  tendency  to 
construct  all  Diesel  engines,  land  and  marine,  except  those 
developing  50  H.P.  or  less  per  cylinder,  as  crosshead  type  engines, 


516  PRACTICE  OF  LUBRICATION 

because  there  is  less  trouble  with  piston  distortion,  the  crosshead 
bearing  can  be  kept  cool,  being  remote  from  the  piston;  car- 
bonized dirty  oil  from  the  piston  may  be  prevented  from  reaching 
the  crank  chamber,  and  the  oil  in  the  crank  chamber  can  be 
prevented  from  reaching  the  cylinders;  it  is  kept  cooler  and  cleaner 
and  therefore  retains  its  vitality  much  longer. 

Most  auxiliary  Diesel  engines  and  other  high  speed  engines 
are  of  the  trunk  piston  type  and  of  necessity  always  entirely 
enclosed.  The  pistons,  when  above  say  18  in.  in  diameter,  are 
always  built  in  two  parts,  a  plate  being  inserted  between  the  top 
and  the  bottom  portion,  which  prevents  oil  from  the  gudgeon  pin 
splashing  into  the  hot,  hollow  piston  head,  where  it  would  burn 
and  char. 

Two-stroke  cycle  engines  are  more  difficult  to  lubricate  than 
four-stroke  engines.  The  pressure  is  never  relieved  on  the  mov- 
ing parts,  making  it  difficult  for  the  oil  to  get  in  between  the 
bearing  surfaces.  The  long  trunk  pistons  needed  to  close  the 
scavenging  and  exhaust  ports  have  large  friction  surfaces  and 
are  more  liable  to  wear  and  seizure  than  the  pistons  in  crosshead 
type  engines.  Two-stroke  engines  may  be  constructed  with 
crossheads,  but  it  makes  a  very  tall  engine,  as  the  long  trunk 
pistons  must  be  retained. 

Cooling. — The  piston  head  in  larger  engines  is  frequently  built 
with  provision  made  for  cooling,  the  cooling  medium  being 
either  oil  or  fresh  water.  The  cooling  water  for  the  pistons  must 
be  fresh  water;  sea  water  is  liable  to  deposit  salt  incrustations 
inside  the  pistons.  In  navigating  in  muddy  or  shallow  waters,  it 
is  obvious  that  such  water  is  totally  unsuitable  for  piston  cooling 
purposes.  It  is  bad  enough  for  the  cylinder  jackets  and  for 
cooling  the  piston  cooling  water;  and  as  incrustations,  scale  or 
mud,  greatly  reduce  the  heat  transmission,  all  cooling  spaces 
must  be  so  designed  that  they  can  be  easily  examined  and  cleaned, 
which  should  be  done,  say  every  three  months. 

In  shutting  down  the  engine,  cooling  of  the  pistons  and  cylin- 
ders must  be  continued  for  half-an-hour  to  prevent  boiling  of  the 
water  and  formation  of  deposits  of  salt,  lime,  etc.  This  is  particu- 
larly important  where  hard  water  or  sea  water  is  used,  and  also 
with  piston  cooling  oil  in  marine  Diesel  engines,  as  the  oil  is 
cooled  by  sea  water  and  it  is  not  always  possible  to  guard  against 
leakage  of  a  little  sea  water  into  the  cooling  oil.  Leakage  from 
the  joints  or  telescopic  pipes  carrying  water  or  oil  into  the  piston 
is  difficult,  almost  impossible,'  to  avoid.  If  cooling  water  gets 
into  the  oil  it  may  cause  emulsification  in  the  same  way  as  water 
in  turbine  oil.  Leakage  of  cooling  oil  into  the  lubricating  oil 


DIESEL  ENGINES,  LAND  AND  MARINE 


517 


system  is  not  so  serious,  but  if  cooling  oil  is  very  thin,  it  may  in 
time  reduce  the  viscosity  of  the  lubricating  oil  sufficiently  to  be 
noticeable. 


PRINCIPLE  OF  OPERATION  OF  DIESEL  ENGINES 

In  the  Diesel  engine  fuel  is  injected  into  the  cylinder  and  is 
directly  converted  into  power.  It  operates  on  either  the  four- 
stroke  cycle  or  the  two-stroke  cycle  principle,  as  follows: 

Four-stroke  Cycle  (Fig.  201). 

First  Stroke  (Suction). — The  piston  moves  downwards  away  from  the 
cylinder  head,  sucking  in  air  through  the  open  air  inlet  valve.  Exhaust  valve 
and  fuel  vcdvz  are  closed. 


First  Stroke  Second  Stroke  Third  Stroke  Fourth  Stroke 

Suction  Compression  Power  Exhaust 

FIG.  201. — Four  stroke  cycle  principle  of  operation,  Diesel  engines. 

Second  Stroke  (Compression). — The  piston  moving  upward  toward^  the 
cylinder  head  compresses  the  air  to  a  pressure  of  about  500  pounds,  resulting 
in  a  temperature  of  about  1000°F.,  which  is  sufficient  to  ignite  and  burn  the 
fuel. 

Air  inlet  valve,  exhaust  valve  and  fuel  valve  are  closed. 

Third  Stroke  (Power). — The  fuel  valve  opens;  fuel  is  blown  in  the  form  of 
a  fine  spray  into  the  cylinder  by  means  of  the  highly  compressed  air  coming 
from  the  air  reservoirs.  There  is  no  explosion,  but  the  fuel,  due  to  the  high 
temperature  existing  in  the  cylinder,  burns  completely  as  it  enters,  main- 
taining a  constant  pressure  during  fuel  injection.  The  fuel  valve  is  then 
closed;  the  expanding  gases  force  the  piston  away  from  the  cylinder  cover 
during  the  power  stroke,  all  wilves  being  closed. 

Fourth  Stroke  (Exhaust). — The  piston,  moving  upwards  towards  the  cylin- 
der cover,  drives  out  the  burned  gases  through  the  open  exhaust  valve. 
Air  inlet  valve  and  fuel  valve  are  closed. 


518 


PRACTICE  OF  LUBRICATION 


Thus  four  strokes  of  the  piston,  i.e.  one  power  stroke  followed 
by  three  idle  strokes,  complete  the  cycle  of  events. 

Two-Stroke  Cycle  (Fig.  202). 

Fi.st  Stroke  (Compression). — At  the  beginning  of  the  stroke,  the  piston 
has  uncovered  the  exhaust  ports  through  which  the  burned  gases  are 
expelled,  the  scavenging  air  entering  either  through  the  scavenging  valves 
in  the  cylinder  cover,  or  through  the  scavenging  ports  in  the  cylinder;  the 
piston,  rising,  covers  the  exhaust  ports.  The  scavenging  valve  or  ports  are 
closed  and  the  air  is  compressed  to  a  pressure  of  about  500  pounds. 

Second  Stroke  (Power). — At  the  top  of  the  piston  stroke,  fuel  is  sprayed 
into  the  cylinder  and  the  piston  descends  on  its  power  stroke. 


First  Stroke  Second  Stroke 

FIG.  202. — Two  stroke  cycle  principle  of  operation,   Diesel  engines. 

Towards  the  end  of  the  stroke  the  piston  uncovers  the  exhaust  ports  and 
the  exhaust  gases  escape,  being  assisted  by  the  scavenging  air  blown  into 
the  cylinder  through  the  scavenging  valves  or  ports. 

Thus  two  strokes  of  the  piston,  i.e.,  a  compression  stroke  fol- 
lowed by  a  power  stroke,  complete  the  cycle  of  events. 

Starting. — The  Diesel  engine  is  always  started  by  means  of 
compressed  air.  The  starting  air  reservoirs  are  filled  with  com- 
pressed air,  usually  at  a  pressure  of  350  pounds;  occasionally 
higher  pressures  are  employed.  This  pressure  should  never  fall 
as  low  as  200  pounds.  Starting  air  is  delivered  to  the  starting 
air  reservoirs  either  from  an  auxiliary  air  compressor  or  it  is 
taken  from  the  injection  air  bottles.  "  A  pipe  conveys  the^air 
from  the  starting  air  storage  bottle  to  the  starting  valve  casings. 
The  starting  valves  in  all  cylinders  are  automatically  opened 


DIESEL  ENGINES,  LAND  AND  MARINE  519 

and  closed,  so  that  the  starting  air  is  admitted  only  into  lho.sc 
cylinders  in  which  the  pistons  are  in  the  right  position  for  their 
downward  strokes. 

When  the  engine  has  made  a  few  revolutions  by  means  of 
compressed  air,  the  fuel  pump  is  put  into  service.  .  The  starting 
handle  which  throws  the  fuel  pump  into  automatic  service,  throws 
the  starting  air  valves  out  of  service.  , 

In  the  case  of  two-stroke  cycle  engines,  starting  is  occasionally 
performed  by  admitting  compressed  air  into  the  scavenging  pump 
cylinders.  The  resultant  motion  of  the  scavenging  pump  is 
transmitted  through  levers  to  the  main  engine  crosshead. 

Reversing.  —  For  the  purpose  of  reversing  marine  engines, 
two  sets  of  cams  are  employed;  " ahead  cams"  and  " astern 
cams."  For  going  ahead,  "ahead  cams"  are  in  action,  operating 
all  valves;  for  going  astern,  "astern  cams"  are  put  into  action, 
controlling  the  operation  of  the  valves.  The  necessary  altera- 
tions in  the  position  of  the  cam  shafts  when  reversing  are  carried 
out  by  means  of  compressed  air  or  in  the  case  of  smaller  engines, 
by  hand. 

FUEL 
The  fuels  in  use  are: 

Gas  oil. 

Black  fuel  oil. 

Coal'tar  oil  or  Lignite  tar  oil. 

Coal  tar. 

Vegetable  oils  and  Animal  oils. 

Gas  Oil. — Gas  oils  are  excellent  fuels  for  Diesel  engines  but 
are  more  expensive  than  black  fuel  oils. 

Black  Fuel  Oil. — Fuel  oils  (see  page  504)  for  Diesel  purposes 
must  not  be  too  viscous;  if  they  are  too  viscous  at  the  tempera- 
ture prevailing  in  the  fuel  valve  space,  they  are  badly  atomized. 
Fuel  oils  of  a  Saybolt  viscosity,  say,  less  than  200"  at  104°F. 
will  normally  be  found  to  atomize  readily. 

Coal  Tar  Oil  and  Lignite  Tar  Oil  are  produced  from  bituminous 
coal  and  lignite,  respectively,  the  distillation  being  directed 
with  a  view  to  producing  a  suitable  quality  of  tar  oil  for  Diesel 
engines.  Usually  a  small  percentage  of  gas  oil  or*  other  light 
petroleum  fuel  oil  is  injected  into  the  Diesel  engme'cylinder  by 
an  ignition  oil  pump,  just  before  the  tar  oil  is  sprayed  in,  by 
means  of  the  fuel  pump.  The  burning  gas  oil  helps  to  ignite 
the  atomized  tar  oil,  so  that  it  burns  completely  without 
"sooting." 


520  PRACTICE  OF  LUBRICATION 

Coal  Tar  when  produced  from  bituminous  COM!  in  vertical 
retorts  can  sometimes  be  used,  but  it  must  be  heated  in  order  to 
flow  freely  and  can  be  employed  only  with  the  addition  of  about 

10  per  cent,  of  light  petroleum  fuel  oil  used  in  the  same  manner 
as  described  under  tar  oil. 

Vegetable  and  Animal  Oils,  such  as  castor  oil,  palm  oil,  earth 
nut  oil,  cottonseed  oil,  whale  oil,  etc.,  can  also  be  used  as  fuel  in 
Diesel  engines,  and  may  come  into  consideration  for  tropical 
countries  where  there  is  no  easy  access  to  other  fuels. 

Fuel  Storage,  etc. — When  the  fuel  is  pumped  from  the  storage 
tanks  it  should  be  carefully  strained  before  entering  the  daily 
supply  tanks.  The  latter  are  fitted  with  a  drain  pipe  for  remov- 
ing water  which  may  accumulate.  The  fuel  delivery  is  taken 
from  the  daily  supply  tank  at  a  height  of,  say,  10  inches  above 
the  bottom,  so  that  only  clean  fuel  passes  down  through  this 
pipe  and  through  an  additional  filter  to  the  fuel  pump. 

When  the  engine  has  been  carefully  adjusted  to  suit  a  particular 
class  of  fuel,  it  is  very  important  that  the  fuel  supplies  should  be 
as  uniform  in  quality  as  possible,  in  order  to  obtain  highest  effici- 
ency and  to  obviate  the  necessity  of  further  adjustment;  other- 
wise, incomplete  combustion  will  take  place  and  will  interfere 
with  lubrication. 

METHODS  OF  LUBRICATION 

Trunk  piston,  enclosed  type  Diesel  engines,  land  and  marine, 
are  always  lubricated  by  a  full  force  feed  circulation  system,  the 

011  being  circulated  under  a  pressure  of  up  to  25  pounds  per  square 
inch,  depending  upon  the  size  of  the  engine. 

Trunk  piston,  open  type,  land  engines  have  all  parts  lubricated 
from  mechanically  operated  lubricators,  except  the  main  bear- 
ings, which  are  always  ring  oiled. 

Crosshead  Type  Diesel  Engines,  Land  and  Marine. — The 
piston  lubrication  is  always  by  means  of  a  mechanically  operated 
lubricator. 

The  external  parts  are  lubricated  by  means  of: 

(a)  Force  feed  circulation,  all  parts  enclosed. 

Most  marine  engines  (Burmeister  &  Wain  type)  em- 
ploy this  system. 

(b)  Oil  distribution  by  gravity  feed  or  by  mechanically  operated 
lubricators  to  all  parts. 

Most   large    two-stroke    cycle    Diesel   engines    employ 
these  systems;  also  some  four-stroke  cycle  marine  engines. 

Piston  Lubrication. — The  oil  feeds  from  the  mechanical  lubri- 
cator should  preferably  be  timed  to  inject  the  oil  at  the  right 


DIESEL  ENGINES,  LAND  AND  MARINE 


521 


moment.  It  is  often  convenient  to.  have  the  lubricators  arranged 
for  a  rotary  drive,  the  cams  or  levers  inside  the  lubricator  being 
so  placed  as  to  operate  their  respective  plungers  at  the  right 
moment  for  their  respective  pistons. 

One  method  which  is  much  used  is  to  have  one  lubricator  for 
each  cylinder  unit,  all  pumps  operated  simultaneously  by  means 
of  an  oscillating  lever,  actuated  by  a  cam  on  the  camshaft  or  by 
some  other  part  having  a  reciprocating  motion. 

For  pistons  up  to  20  in  .-22  in.  in  diameter,  two  separate  oil 
feeds,  one  at  the  front  and  one  at  the  back  are  sufficient;  for 
larger  pistons  four  oil  inlets  are  preferred. 

Fig.  203  shows  an  oil  injector  for  timed  injection  of  the  oil 
through  a  small  hole  on  to  the  piston.  With  a  large  oil  hole  it 
is  obviously  not  possible  to  get  a  satisfactory  timing  effect. 


FIG.  203.— Oil  injector. 

Force  Feed  Circulation  (referring  to  all  types  of  engines, 
employing  this  system).  The  strainers  for  the  oil  should  be  in 
duplicate.  When  one  of  the  strainers  is  removed  for  examination 
or  cleaning,  the  oil  pump  connection  from  that  particular 
strainer  should  be  automatically  closed  by  a  spring  loaded  valve, 
which  is  pushed  open  again  when  the  strainer  is  put  back  in 
position. 

Some  makers  instal  a  filter — filter  pads,  sand  filters,  etc.— 
somewhere  in  the  circuit.  They  are  of  doubtful  value  as  re- 
gards extracting  carbon  particles  and  may  absorb  a  great  deal 
of  power. 

With  a  Diesel  engine,  as  with  all  internal  combustion  engines, 
the  bearings  are  subject  to  full  pressure  almost  from  the  starting 
moment.  A  hand  pump  should  therefore  be  provided  to  prime 
the  oil  pipes  before  starting  the  engine.  Many  bearing  troubles 
are  caused  by  injury  done  to  the  surfaces,  due  to  absence  of  oil 


522  PRACTICE  OF  LUBRICATION 

in  the  bearings  when  the  engine  is  started  up  before  the  oil  pipes 
are  primed. 

Oil  Temperature. — Heat  radiated  from  the  pistons  and  cylinder 
walls  is,  to  a  large  degree,  retained  in  the  enclosed  crank  chamber, 
so  that  the  oil  in  the  crank  chamber  becomes  very  warm,  the 
resulting  temperature  being  from  100°F.  to  160°F.  If  a  tem- 
perature of  140°F.  be  greatly  exceeded,  the  life  of  the  oil  will  be 
much  reduced,  and  it  will  oxidize  and  throw  down  a  dark  deposit. 

In  large  marine  Diesel  engines  in  Merchant  Marine  service, 
the  quantity  of  oil  in  circulation  is  large,  being  about  one  gallon 
per  horse  power.  For  this  reason,  special  cooling  of  the  oil  is 
not  always  needed,  particularly  so  as  the  engine  room  temperature 
is  low  as  compared  with  the  temperature  in  the  engine  room  of  a 
steamship,  where  the  hot  steam  cylinders  and  pipes  radiate 
much  heat. 

In  naval  craft,  such  as  submarines,  owing  to  the  limited  space, 
the  Diesel  engines  are  very  compactly  designed,  all  parts  being 
cut  down  in  weight  to  the  minimum.  This,  fact,  combined  with 
the  high  speed  of  revolutions  and  the  relatively  high  temperature 
of  the  engine  room,  produces  high  oil  temperature  and  makes  it 
imperative  to  provide  for  adequate  and  efficient  cooling  of  the 
oil  in  circulation. 

Distribution  of  Oil  by  Gravity  or  by  Mechanical  Lubricators.— 
Two -stroke  cycle  marine  Diesel  engines,  notably  those  of  German 
make,  have  experienced  a  great  deal  of  trouble  with  heating  and 
heavy  wear  of  main  bearings  (bottom  halves),  crank  pin  bearings 
(top  halves),  and  crosshead  bearings.  One  of  the  main  reasons 
for  these  troubles  has  been  the  use  of  gravity  feed  circulation 
systems  embodying  a  filtering  arrangement  which  necessitated 
the  use  of  straight  mineral  oils.  Owing  to  the  severe  pressures 
very  heavy  viscosity  oils  had  to  be  employed,  which  were  too 
viscous  to  filter  properly  (cold  engine  rooms)  and  were  found 
incapable  of  withstanding  the  high  unrelieved  bearing  pressures. 
As  far  as  the  crosshead  bearing  is  concerned,  the  difficulty  is 
entirely  overcome  by  forcing  the  oil  in  between  the  bearing 
surfaces  by  means  of  a  small  plunger  pump  fixed  on  the  crosshead 
and  operated  by  the  swinging  motion  of  the  connecting  rod. 
Improved  distribution  of  the  oil  in  the  crank  pin  bearings  and 
main  bearings  has  been  obtained  by  having  narrow  "flats"  on 
the  revolving  journals  which  receive  the  oil  and  help  to  distribute 
it  to  the  bearing  parts  under  pressure. 

The  most  effective  solution  of  the  problem  is,  however,  to  use 
oils,  heavily  compounded  with  fixed  oil,  such  as  rape  oil,  blown 
rape  oil  or  the  like,  to  the  extent  of  15  per  cent,  to  25  per  cent. 


DIESEL  ENGINES,  LAND  AND  MARINE  523 

of  fixed  oil.  The  mineral  base  should  have  a  low  setting  point,  so 
that  the  compounded  oil  will  combine  great  oiliness  with  satis- 
factory fluidity  at  all  times,  even  in  the  cold.  An  oil  of  this 
character  will  feed  more  uniformly  through  gravity  feed  or 
syphon  oilers  than  oils  having  a  higher  setting  point  and 
viscosity.  Such  compounded  oils  cannot  very  well  be  used  in  a 
circulation  system,  but  can  be  applied  in  a  gravity  feed  system, 
or,  if  great  economy  is  desired,  by  a  mechanically  operated  lubri- 
cator. The  oil,  when  leaving  the  bearings,  is  usually  run  to 
waste  into  the  bilges. 

In  the  few  two-stroke  marine  Diesel  engines  built  in  England, 
compounded  engine  oils  have  been  used  for  bearings  and  have 
given  complete  satisfaction.  One  maker  finds  that  with  a  com- 
pounded engine  oil,  there  is  even  no  need  to  force  the  oil  into  the 
crosshead  bearing  by  a  special  pump.  The  oil  wedges  itself  in 
between  the  surfaces  without  any  apparent  difficulty.  Another 
point  in  favor  of  compounded  oil  is  that  if  water  at  any  time 
should  be  needed  to  cool  a  bearing,  the  water  will  not  wash  away 
the  compounded  oil,  but  might  easily  do  so  with  a  straight  mineral 
oil. 

Oil  Consumption. — The  oil  consumption  of  Diesel  engines 
ranges  from  .75  to  5.0  grams  per  B.H.P.  hour.  The  lowest 
oil  consumption  is  obtained  with  large  four-stroke  cycle  Diesel 
engines  of  the  crosshead,  enclosed  type,  employing  force-feed 
circulation.  The  following  oil  consumption  is  typical  of  such 
engines : 

Cylinders 15  grams  per  B.H.P.  hr. 

Force  feed  circulation  system .60  grams  per  B.H.P.  hr. 

Air  compressors 05  grams  per  B.H.P.  hr. 

The  oil  consumption  in  the  force  feed  circulation  system  in- 
creases greatly  in  Diesel  ships  when 'going  through  the  Tropics, 
as,,  due  to  the  higher  oil  temperature,  the  oil  becomes  thinner, 
which  means  more  oil  spray,  more  oil  creeping  and  more  leakage 
through  joints. 

Smaller  Diesel  engines  use  more  oil  per  B.H.  P.  hour  than  large 
engines.  The  small  open  type  engines  do  so  because  the  high 
R.P.M.  throws  the  oil  into  the  engine  room,  and  with  the  enclosed 
trunk  piston  type  engines  it  is  difficult  to  avoid  excess  oil  passing 
to  the  piston  tops,  where  it  burns  and  chars. 

In  open  type  land  engines  the  waste  oil  should  be  collected 
and  kept  in  large  settling  tanks,  containing  several  hundred 
gallons  of  oil,  so  that  the  oil  slowly  frees  itself  from  the  exceedingly 
fine  carbonaceous  matter  by  the  force  of  gravity  alone.  Filtering 


524  PRACTICE  OF  LUBRICATION 

the  oil  in  the  ordinary  way  is  useless,  as  the  pores  and  interstices 
in  any  filtering  material  are  like  tunnels  for  the  fine  carbon 
particles  which  therefore  cannot  be  retained.  An  apparatus 
to  free  the  waste  oil  from  carbon  is  described  page  554.  Fig.  217. 

In  enclosed  trunk  piston  type  engines  the  fitting  of  splashguards 
over  the  crank  webs,  the  pegging  of  piston  rings,  and  maintaining 
a  reasonable  oil  pressure  are  points  to  keep  in  mind  when  the 
oil  consumption  is  excessive. 

In  average  size  Diesel  engines,  250  to  500  H.P.,  the  oil  con- 
sumption if  given  reasonable  attention  should  not  exceed  from 
2.0  to  3.0  grams  per  B.H.P.  hour,  but  will  rarely  be  as  low  as 
1.0  gram  per  B.H.P.  hour. 

Carbon  Deposits. — Carbon  deposits  may  be  caused  by  over- 
feeding of  oil,  the  use  of  an  unsuitable  oil,  impurities  in  the  intake 
air,  impurities  in  the  fuel,  unsuitable  fuel  or  incomplete  combus- 
tion. The  first  three  causes  are  exactly  similar  to  those  men- 
tioned for  gas  engines,  except  that  with  marine  Diesel  engines 
the  intake  air  is  nearly  always  pure,  but  is  has  been  known  to 
carry  with  it  fine  sea  water  spray  in  suspension  into  the  engine, 
producing  salt  deposits  and  rapid  wear. 

Impurities  in  the  Fuel. — When  the  fuel  oil  contains  too  much 
free  carbon  or  ash,  the  unburned  impurities  will  deposit  them- 
selves on  the  cylinder  walls,  adhering  to  the  lubricating  oil  and 
forming  a  deposit  which  will  result  in  heavy  wear  of  cylinder 
walls  and  piston  rings.  Too  much  water  in  the  fuel  will  cause 
irregular  fuel  charges  and  interfere  with  proper  combustion, 
the  result  being  irregular  running  and  even  misfiring.  Water 
in  the  fuel  also  attacks  the  fuel  valve  and  its  valve  seat,  causing 
cutting  and  fuel  leakage. 

Sulphur  does  not  appear  to  affect  the  lubrication  of  Diesel 
Engines. 

Unsuitable  Fuel. — A  fuel  containing  too  much  asphaltum  or 
too  thick  to  flow  readily  will  not  be  properly  atomized  when 
injected  through  the  fuel  valve,  and  does  not  burn  completely 
during  combusiton;  the  unburned  portions  will  accumulate  on 
the  piston  top,  behind  and  between  the  piston  rings,  etc.,  and 
form  carbonaceous  deposits. 

Incomplete  Combustion. — Correct  proportion  of  injection  air 
to  the  fuel  used  is  important,  in  order  to  obtain  complete  com- 
bustion. Incomplete  combustion  may  be  due  to  the  blast 
pressure  being  too  high  or  too  low,  to  the  fuel  valve  being  out 
of  order,  or  to  the  use  of  an  unsuitable  fuel. 

Blast  pressures  too  high  for  the  load,  which  is  particularly 
likely  to  occur  under  light  load  conditions  or  when  starting  the 


DIESEL  ENGINES,  LAND  AND  MARINE  525 

engine,  result  in  too  much  air  passing  through  the  fuel  valve. 
Owing  to  the  great  fall  in  pressure,  the  expansion,  resulting  in 
cooling,  will  cool  the  fuel  spray,  so  that  the  fuel  is  incompletely 
burned.  The  unburned  portions  deposit  themselves  on  the 
piston  tops,  and  every  few  strokes  the  accumulated  fuel  will 
spontaneously  ignite  when  the  piston  rises  on  the  compression 
stroke,  causing  preignition  and  violent  knocking. 

If  the  blast  pressure  is  too  low,  imperfect  atomization  of  the 
fuel  produces  deposits  due  to  the  larger  particles  of  fuel  in  the 
spray  not  being  completely  burned.  With  incomplete  combus- 
tion the  exhaust  will  be  black. 

Fuel  valve  out  of  order  will  result  in  incomplete  combustion, 
due  to  fuel  leakage  into  the  cylinder  during  the  exhaust,  suction, 
and  compression  strokes  of  the  piston.  Preignition  of  the  accumu- 
lated fuel  on  the  top  of  the  piston  will  take  place  at  the  end 
of  the  compression  stroke  and  cause  knocking.  The  constant- 
leakage  of  injection  air  through  the  fuel  valve  will  result  in  cut- 
ting and  destruction  of  the  fuel  valve  and  its  seat. 

DIESEL  ENGINE  AIR  COMPRESSORS 

The  air  compressor  which  supplies  air  at  high  pressure  for  the 
fuel  injection  is  in  land  Diesel  engines  usually  built  as  part  of 
the  engine,  being  driven  from  the  main  crank  shaft;  but  in  marine 
Diesel  engines  it  is  sometimes  driven  by  an  auxiliary  high  speed 
Diesel  engine.  The  air  compressor  in  two-stroke  cycle  Diesel 
engines  usually  draws  its  air  from  the  scavenging  air  supply. 

In  land  Diesel  engines  below  500  H.P.  and  marine  engines 
below  300  H.P.  the  air  compressors  are  usually  of  the  two-stage 
type,  but  many  manufacturers  fit  three-stage  air  compressors, 
even  for  small-sized  engines,  the  tendency  being  to  abandon  the 
two-stage  type,  in  order  to  obtain  lower  temperature  of  the  air 
leaving  the  compressor.  The  air  compressor  in  Diesel  engines 
above  500  horse  power  is  practically  always  three-stage,  or  for 
marine  service  even  four-stage. 

PRESSURE  DISTRIBUTION  IN  Two-  AND  THREE-STAGE  AIR  COMPRESSORS 

Gauge    pressure, 
Ibs.  per  sq.  in. 

Two-stage.        Leaving  1st  stage 120  to  150 

Leaving  2nd  stage 900  to  1000 

Tkr.'C-stagc-.      Leaving  1st  stage 40  to  60 

Leaving  2nd  stage 120  to  220 

Leaving  3rd  stage 900  to  1000 


526  PRACTICE  OF  LUBRICATION 

Air  Compressor  Lubrication. — The  internal  lubrication  of  the 
air  compressor  is  considered  an  important  feature  in  connection 
with  the  lubrication  of  Diesel  engines.  The  oil  is  here  subject 
to  oxidation  from  the  compressed,  highly  heated  air. 

If  an  excess  amount  of  oil,  or  an  unsuitable  oil  is  used,  the 
result  of  oxidation  is  the  formation  of  carbon  deposits  which 
accumulate  principally  on  the  pistons,  on  the  valves,  and  in  the 
discharge  pipes.  The  valves  work  at  high  speed,  and  even  a 
slight  deposit  may  cause  them  to  work  sluggishly  or  to  stick. 
Under  these  conditions  the  air  is  wire  drawn  and  recompressed 
through  the  delivery  valves,  the  hot  air  heats  the  valves  and  the 
temperature  may  easily  rise  to,  say,  700°F  -800°F.  or  more  which 
is  above  the  spontaneous  ignition  temperature  of  a  mixture  of 
oil  vapour  and  air.  The  deposit  now  becomes  incandescent  and 
any  accumulated  oil  will  vaporize  and  explode.  Restricted 
openings  in  discharge  pipes  will  have  the  same  effect.  It  is 
therefore  necessary  to  use  only  the  very  best  oil,  one  which  has 
only  a  slight  tendency  to  carbonize. 

The  oil  must  be  fed  sparingly  and  uniformly,  preferably  by 
means  of  a  mechanically  operated  lubricator,  to  the  low-pressure 
piston.  The  air  usually  carries  sufficient  oil  from  the  low-pres- 
sure stage  to  lubricate  also  the  intermediate  and  high-pressure 
pistons,  but  in  large  compressors  these  pistons  may  have  to  be 
lubricated  direct  as  well. 

The  intercoolers  and  oil  separators  should  be  drained  regularly 
and  frequently  enough  to  prevent  the  accumulaton  of  oil  or  water 
being  carried  over  to  the  last  stage  air  cylinder  where  the  water 
might  cause  the  cylinder  to  burst. 

It  is  perhaps  safe  to  say  that  over  half  the  troubles  experienced 
with  Diesel  engines  have  been  in  connection  with  the  air  com- 
pressors; and  the  general  feeling  is,  quite  correctly,  that  the 
quality  of  the  oil  and  the  quantity  used  are  chiefly  responsible. 
This  whole  question  therefore  demands  a  thorough  analysis. 

Dust  has  been  responsible  for  carbon  deposit  and  is  usually 
easy  to  discover  by  chemical  analysis  of  the  deposit. 

Inefficient  cooling  of  air  compressor  cylinders  or  valve  casings 
has  been  responsible  for  a  good  deal  of  carbonization  trouble; 
the  water  spaces  have  become  incrustated  with  scale  or  mud  from 
the  water,  or  the  water  supply  has  been  too  scanty,  causing  high 
temperatures  of  the  discharge  valves,  etc. 

Fuel  oil  getting  in  with  the  intake  air  will  almost  certainly 
lead  to  the  formation  of  deposits. 

'Oil  spray  in  the  intake  air  may  be  the  cause  of  carbonization 
when  the  air  compressor  take  its  air  supply  from  the  crank 


DIESEL  ENGINES,  LAND  AND  MARINE  527 

,   in  which   the  air  is  rlmrjrrd   with   finely  atomized  oil 


spray. 

Too  infrequent  drainage  of  intercoolers  allows  water  to  be 
carried  over  to  the  smaller  dimension  higher  stage  cylinders. 
The  clearance  space  in  the  H.P.  compressor  cylinder  is  so  small 
that  it  is  easily  filled  with  water  from  the  preceding  intercooler  ; 
the  water  cannot  escape  through  the  discharge  valve  quickly 
enough  and  so  the  cylinder  is  fractured. 

Intercoolers  should  be  fitted  with  relief  valves,  big  enough  to 
allow  all  of  the  air  coming  from  the  preceding  cylinder  to  blow 
off,  if  the  suction  valves  in  the  succeeding  cylinder  are  choked; 
otherwise  the  intercooler  will  burst. 

Aftercoolers  and  blast  vessels  should  be  drained  at  intervals. 
Accumulated  oil  has  been  ignited  and  exploded  by  high  tempera- 
ture caused  by  a  semi-choked  discharge  valve  or  pipe  on  the  H.P. 
compressor  cylinder,  or  by  back  fire  from  the  engine  cylinder, 
and  particularly  when  oxygen  has  been  used  to  recharge  the 
blast  vessels.  This  latter  practice  is  now  condemned.  Of  course, 
such  accumulation  of  oil  ought  not  to  occur  and  will  not  occur  with 
sufficiently  frequent  drainage. 

Too  small  number  of  compression  stages  means  excessive  air 
temperature  and  increased  tendency  to  carbonize  the  oil.  Under 
light  load  conditions  some  air  compressors  throttle  the  air  intake, 
with  the  result  that  the  air  is  really  compressed  in  one  stage 
less  and  therefore  becomes  much  hotter  than  under  full  load 
conditions. 

Excessive  oil  consumption  is  responsible  for  many  cases  of 
heavy  carbonization.  Where  air  compressors  have  L.P.  trunk 
pistons  lubricated  by  oil  from  the  force  feed  circulation  system, 
oil  may  pass  the  L.P.  piston  in  large  quantities.  The  piston  rings 
should  be  pegged,  and  splash  guards  may  be  fitted  to  prevent 
excessive  splashing  to  the  cylinder  walls.  But  the  amount  of  oil 
needed  for  air  compressor  lubrication  is  small,  much  smaller  than 
the  minimum  consumption  obtainable  under  the  conditions  just 
described.  It  is  therefore  better  to  design  the  air  compressor  so 
that  it  can  be  separately  and  economically  lubricated,  only 
receiving  the  amount  of  oil  actually  needed. 

There  is  another  reason  why  the  oil  consumption  should  be 
reduced  to  a  minimum.  All  the  oil  which  passes  through  the 
compressor  is  subject  to  the  oxidizing  effect  of  the  air,  and  conse- 
quently the  unsaturated  hydrocarbons  and  perhaps  some  of.  the 
more  easily  decomposed  saturated  hydrocarbons  as  well  combine 
with  oxygen,  partly  decompose  and  form  petroleum  acid,  which 
is  said  to  assist  in  the  thinning  of  the  copper  tubes  in  the  coolers, 


528  PRACTICE  OF  LUBRICATION 

particularly  those  in  the  after  cooler.  As  a  confirmation  of  this 
explanation  one  maker  found  that  when  he  introduced  mechan- 
ically operated  lubricators  for  the  compressors,  feeding  the  oil 
sparingly  to  the  L.P.  stage  only,  the  life  of  the  cooler  tubes  was 
much  prolonged — due  to  less  oil  passing  through  the  compressor 
and  therefore  less  acid  being  formed  by  oxidation. 

It  is  possible  that  galvanic  action  may  assist  in  corroding  the 
pipes.  In  the  after  portion  of  the  coil,  where  the  moisture  con- 
denses, the  copper  is  covered  with  water,  which  is  slightly  acid, 
and  as  the  coils  are  joined  to  steel  covers  we  have  here  the  three 
factors  needed  for  galvanic  action. 

The  chief  cause  of  the  thinning  of  the  pipes  is,  probably  the 
condensed  moisture  in  the  compressed  air,  and  it  must  not  be 
overlooked  that  air  at  80  atm.  pressure  is  very  dense  and  in 
rushing  through  the  pipes  creates  great  friction,  which  assists  in 
eroding  the  soft  copper  surfaces. 

Air  Compressor  Oil. — In  view  of  the  foregoing  facts,  the  ques- 
tion that  remains  to  be  answered  is :  what  kind  of  oil  should  be 
used  to  minimize  the  danger  of  explosion? 

Formation  of  carbon'  deposit  is  obviously  at  the  root  of  the 
problem,  because  if  no  carbon  were  formed,  there  would,  nor- 
mally, be  no  excessive  temperatures,  at  any  rate  not  high  enough 
to  vaporize  or  to  explode  accumulated  oil,  which,  by  the  way, 
ought  not  to  be  there.  Feeding  the  oil  economically  by  a  me- 
chanically operated  lubricator  reduces  oil  consumption,  and 
therefore  means  less  carbon  deposit  and  less  acidity  in  the  water 
separating  out  in  the  coolers  and  purgepots. 

But  the  character  of  the  oil  is  of  very  great  importance.  About 
ten  years  ago  the  author  introduced  for  the  first  time  a  com- 
pounded oil  (containing  three  per  cent,  of  animal  oil)  for  Diesel, 
compressors,  and  the  results  were  that  compressors  would  operate 
with  perfectly  dean  valves  and  pistons  sometimes  for  periods 
extending  over  several  months  and  notwithstanding  rather  exces- 
sive oil  feed.  The  explanation  appears  to  be  very  simple :  the 
interior  surfaces  of  the  higher  stage  air  cylinders  are  very  wet,  in 
fact  streaming  with  water,  which  tends  to  wash  away  the  oil; 
with  mineral  oil  the  water  succeeds  in  doing  so;  dry  streaks  de- 
velop ;  slight  wear  produces  a  rusty,  spongy  deposit,  which  cakes 
together  with  the  oil  and  sticks  to  the  valve  seats  and  discharge 
pipes,  etc.  This  deposit  attracts  more  oil,  continually  grows, 
and  being  soaked  with  oil  may  bring  about  an  explosion,  as 
explained  on  page  412. 

A  slightly  compounded  oil  will  behave  differently;  it  combines 
with  the  water  and  produces  a  complete  oil  film  on  the  cylinder 


DIESEL  ENGINES,  LAND  AND  MARINE  529 

walls,  exactly  in  the  same  way  as  compounded  steam  cylinder 
oils  give  more  efficient  lubrication  of  steam  engines  employing 
saturated  steam,  and  therefore  can  be  used  very  economically. 

A  suitably  compounded  air  compressor  oil  will  practically 
prevent  cylinder  wear.  There  will  be  no  rust  to  form  nuclei 
for  the  formation  of  carbon  deposits;  the  valves  and  discharge 
pipes  will  keep  clean,  and  high  temperatures  are  avoided.  Such 
an  oil  will  maintain  a  better  seal  on  the  pistons  and  valves  and 
will  therefore  reduce  the  air  leakage  past  pistons  and  valves  which 
always  pr  duces  high  temperatures  of  the  compressed  air. 

The  oil  should  contain  about  3  per  cent,  of  acidless  tallow  oil  or 
prime  lard  oil  which  must  be  practically  free  from  acid.  Three 
per  cent,  lard  oil,  containing  a  fair  amount  of  free  fatty  acid,  or 
even  3  per  cent,  oleic  acid  has  been  used  and  gives  good  results  as 
far  as  freedom  from  carbonization  is  concerned,  but  the  fatty 
acid  attacks  the  copper  tubes  in  the  intercoolers,  and  the  after- 
cooler  in  particular,  forming  large  amounts  of  verdigris  and  causing 
more  rapid  destruction  of  the  tubes  than  when  there  is  no  fatty 
acid  present. 

The  air  compressor  oil  should  have  a  reasonably  high  flash 
point,  not  below  400°F.  nor  above  450°F.  There  is  no  special 
virtue  in  using  a  high  flash  point  oil  as  that  also  means  a  heavy 
viscosity  oil,  which  is  undesirable.  A  sluggish  oil  will  attract 
impurities  that  may  enter  with  the  intake  air  and  it  will  thus 
increase  the  tendency  to  form  deposits.  (See  further  under  Air 
Compressors.) 

Scavenging  Pump. — The  lubrication  presents  no  difficulty,  as 
the  air  is  compressed  only  to  from  3  to  10  pounds.  Air  compres- 
sor oil  should  be  supplied  sparingly  and  uniformly,  preferably 
by  means  of  a  mechanically  operated  lubricator. 

DIESEL  ENGINE  OILS 

The  lubrication  requirements  of  Diesel  engines,  in  normal  op- 
eration, are  very  similar  to  the  requirements  of  vertical  gas 
engines,  and  the  selection  of  suitable  grades  of  oil  follows  similar 
lines,  except  in  the  case  of  marine  Diesel  engines  of  the  large, 
open,  two-stroke  cycle  type,  which,  as  mentioned  page  522, 
require  compounded  bearing  oils  for  external  lubrication.  The 
air  compressor,  wherever  possible,  should  also  be  lubricated  by  a 
slightly  compounded  oil,  unless  the  oil  for  the  compressor  is 
supplied  from  the  Diesel  engine  circulation  system,  in  which  case 
the  compressor  must  make  the  best  of  the  oil  used  in  the  main 
system. 

34 


530 


PRACTICE  OF  LUBRICATION 


Gas  Engine  Oils  Nos.  2,  3,  4,  2c,  3c,  and  4c,  Compressor  Oil 
No.  3c  and  Marine  Engine  Oil  No.  1  are  recommended  by  the 
author  for  lubrication  of  all  types  of  Diesel  eniries,  and  a  rough 
guide  for  selecting  the  correct  grade  is  given  in  lubrication  chart 
No.  19. 

LUBRICATION  CHART  No.  19 
FOR  DIESEL  ENGINES 


Lubrication  system 


Horsepower       Grade  of  oil 
per  cylinder    recommended 


Four-stroke  Cycle   Engines: 

Open    Types: 

For  Cylinders  and  Bearings..  .  . 

Gravity   feed   or   mech- 

Up to  50.     Gas    engine    oil 

anical  lubricator. 

No.  2cor  No.  2. 

For   Cylinders  and  Bearings.  .  . 

Gravity  feed    or   mech- 

Above 50.    Gas     engine   oil 

anical  lubricator. 

No.  3c  or  No.  3. 

Enclosed    Types: 

For  Bearings  only,  crank  cham- 

Force feed  circulation. 

All  sizes.          Circulation 

ber  separated  from  cylinders 

oil    No.  3   or 

by  a  distance  piece. 

Gas  Engine 

oil  No.  3. 

For  Cylinders   only  

Mechanical  lubricator. 

Up  to  50.     Gas    engine    oil 

No.  2c  or  No.  2. 

Above  50. 

Gas    engine    oil 

No.    3c   or    No. 

3. 

For  Cylinders  and  Bearings.  .  .  . 

Force  feed  circulation. 

All  sizes.    Gas     engine    oil 

Trunk    pistons  lubrica- 

No. 3  or  No.    4. 

ted  by  splash  from  crank 

•     ' 

chamber. 

Two-stroke  Cycle  Engines: 
Open  Types: 
For  Cylinders  only 


For  Bearings  only . 


Enclosed  Types: 

For  Cylinders  and  Bearings . 


Mechanical  lubricator.         Up  to  80. 
I  Above  80. 

Gravity  feed  or  mechani-   All  sizes, 
cal    lubricator;    oil    not 
recovered. 

Force      feed    circulation.    All  sizes. 
Trunk  pistons  lubricated 

by    splash    from    crank 

chamber. 


Gas  engine  oil 
No.  3c  or  No.  3. 
Gas  engine  oil 
No.  4c  or  No.  4. 
Marine  engine 
Oil  No.  1. 


Gas   engine   oil 
No.  3  or  No.  4. 


DIESEL  ENGINES,  LAND  AND  MARINE  531 

Grade  of  oil  recommended 

For   Piston  Cooling  of  large   Diesel   Engines,   when 
cooling  oil  is  employed: 

(a)  When  the  cooling  system  is  separate  from  the 

.  lubrication    system Circulation  oil  No.  1. 

(6)  Ditto,  but  joints  leaking  badly Circulation  oil  No.  2 

or  No.  3. 

(c)  When  a  combined  cooling  and  lubrication  sys-  Gas  engine  oil  No.    2 
tern  is  arranged,  the  oil  must  be  a  pure  min-     or  No.  3. 

eral  oil. 
For  Air  Compressors. 

For  the  vast  majority  of  compressors,  in  which  a  Air  compressor  oil  No. 

separate  oil  can  be  fed  to  the  compressor.  3c. 

When  the  air  compressor  cylinders  are  not  separately 
lubricated,  the  oil  supplied  for  the  Diesel  engines 
has  to  be  used,  whether  it  be  straight  mineral  or 
compounded,  but  under  no  circumstances  must 
Marine  engine  oil  No.  1  or  similar  oils  be  used. 
For  Scavenging  Pumps. 

Use  the  same  oil  as  supplied  for  the  air  compressor.} 


BRIEF  NOTES  ON  THE  LUBRICATION  OF  VARIOUS 
WORKS  AND  MACHINERY 

!  CHAPTER  XXXI 
'  STEEL  AND  TINPLATE  MILLS 

In  all  tinplate  mills  (sheet  mills) ,  rolling  tinplate,  and  in  steel 
mills,  rolling  armor  plates  or  very  heavy  "  sections, "  the  roll 
necks  attain  a  very  high  temperature,  from  400°F.  to  700°F. 
Ordinary  oils  will  vaporize  and  leave  the  necks  dry.  Such  necks 
are,  however,  successfully  lubricated  by  so-called  hot  neck  greases, 
which  should  have  high  melting  points  to  suit  the  running  tem- 
peratures of  'the  necks.  The  spent  grease  is  collected,  melted 
in  a  grease  boiler,  mixed  with  a  certain  amount  of  new  grease 
and  " mixing"  grease,  and  can  then  be  used  over  again.  When 
starting  the  mills  cold  on  Monday  mornings,  soft  cold  neck 
grease  is  used  until  the  necks  get  sufficiently  hot  to  allow  the  hot 
neck  grease  to  be  employed.  The  hot  neck  grease  is  applied  hot 
by  a  "swab"  or  when  the  temperatures  are  not  too  high,  in  the 
form  of  strips,  nearly  as  long  as  the  brasses  and  of  a  section  suit- 
able for  the  available  room  between  the  top  and  bottom  brasses. 

In  steel  mills  rolling  not  too  heavy  sections,  the  roll  necks  may 
be  kept  reasonably  cool  by  a  trickle  of  water  running  over  them 
continuously.  An  emulsifying  low  melting  point  grease,  usually 
a  tallow  grease  ("Tallow  Compound"),  should  then  preferably 
be  used,  as  it  gives  excellent  lubrication  and  reduces  the  wear 
considerably,  as  compared  with  hot  neck  greases.  If  the  necks 
cannot  be  kept  cool  enough,  the  tallow  grease  melts  away  too 
quickly  and  hot  neck  greases  may  prove  more  advantageous, 
notwithstanding  the  greater  wear  and  friction. 

Tallow  greases  are  applied  by  placing  a  lump  of  the  grease 
against  the  neck  on  an  inclined  plate  on  both  sides  of  the  bearing 
so  that  it  continuously  tends  to  slide  towards  the  neck.  The 
bottom  roll  necks  frequently  have  no  upper  brasses.  The  tallow 
grease  can  then  be  placed  in  a  sheet  metal  housing  placed  over 
the  neck  and  having  an  opening  in  the  centre  through  which  the 
water  trickles  on  to  the  neck.  Tallow  grease  may  also  be  ap- 
plied in  the  form  of  strips,  as  mentioned  for  hot  neck  greases. 

When  steel  mills  only  roll  light  sections,  the  necks  are  much 

532 


LUBRICATION  OF  VAK1O1  'S  WORKS  AND  MACHINERY         533 

cooler  and  cold  neck  grease  can  'he  used  (No.  2  or  3  Consistency) 
applied  either  direct  to  the  necks  or  in  canvas  bags.  The  grease 
slowly  melts  through  the  bags  and  the  lubrication  is  more  uni- 
form and  more  economical  than  applying  the  grease  direct. 
Soft  tallow  greases  may  also  be  applied  in  bags. 

In  electrically-driven  rolling  mills  the  high  speed  bearings  on 
the  electric  motor  and  the  gear  bearings  are  usually  lubricated 
by  a  force  feed  circulation  system,  using  an  oil  like  Bearing  Oil 
No.  4  or  Circulation  Oil  No.  2. 

For  bearings  which  are  exposed  to  heat,  as  for  example,  bear- 
ings of  hot  metal  cars,  bearings  near  soaking  pits,  etc.,  a  high 
melting  point  soft  or  medium  graphite  grease  will  give  good 
results. 

For  bearings  exposed  to  flame,  as  certain  bearings  in  galvaniz- 
ing machines,  any  oil  burns  immediately  it  is  applied.  The  best 
lubricant  is  finely  powdered  graphite  applied  as  a  powder;  if 
that  is  not  practicable,  it  should  be  applied  mixed  with  oil;  the 
graphite  will  remain  in  the  bearings  and  prevent  undue  wear. 

For  pinions  and  gearing,  cold  neck  grease  is  frequently  used, 
but  it  is  better  and  more  economical  to  use  a  suitable  pinion 
grease.  Good  pinion  greases  are  very  adhesive;  they  should  be 
melted  and  applied  hot  by  a  brush  after  the  teeth  have  been 
previously  cleaned.  The  grease  solidifies  as  a  thin  rubbery 
coating  which  will  preserve  the  teeth  and  assist  towards  getting 
silent  running.  Owing  to  the  great  amount  of  dust  and  dirt 
always  floating  about  in  steelworks  and  tinplate  works,  all  bear- 
ings which  are  lubricated  by  oil  should  have  the  oil  holes  as 
well  protected  as  possible.  Far  too  little  attention  is  generally 
paid  to  this  important  point. 

Bearing  Oil  No.  5  is  a  good  all-round  oil  to  use  in  steelworks 
and  tinplate  works,  but  there  are  many  purposes  for  which  a 
black  oil  of  similar  or  slightly  heavier  viscosity  can  be  used  to 
advantage,  such  as  table  roll  bearings,  shears,  racks,  etc.  For 
mills  in  cold  climates  good  cold  test  is  important,  as  most  of  the 
machinery  is  more  or  less  exposed  to  the  cold  and  draught. 

COLLIERIES 

In  modern  collieries,  steam  turbines,  high  pressure  as  well  as 
exhaust  steam  turbines,  are  largely  used,  and  where  large  coke 
ovens  are  installed,  large  gas  engines  are  often  employed  to  make 
use  of  the  surplus  gas. 

The  fan  engines  are  treated  with  special  care.  The  fans  are 
the  lungs  of  the  mines  and  the  colliery  manager  does  not  change 


534  PRACTICE  OF  LUBRICATION 

oils  or  lubricating  appliances  on  the  fan  engines  unless  he  feels 
pretty  certain  that  the  change  will  prove  beneficial.  The  lubri- 
cation of  the  various  forms  of  power  units,  whether  operated  by 
steam,  gas,  or  electricity,  is  treated  elsewhere  under  their  re- 
spective headings.  The  lubrication  of  steam  haulage  and  winding 
(hoisting)  engines  is  treated  pages  418,  air  operated  engines,  page 
370.  The  lubrication  of  mine  cars  used  in  collieries  is  treated 
specially  pages  320-328. 

Of  other  special  machinery  employed  in  collieries  may  be 
mentioned  coal  cutters  and  screening  plants. 

Coal  Cutters. — There  are  four  principal  types  of  coal  cutters/ 
viz. :  the  disc  cutter,  the  bar  cutter,  the  chain  cutter  and  the  per- 
cussion drill  type.  All  of  these  machines  may  be  operated  either 
by  an  electric  motor  or  by  a  high-speed  air-worked  engine.  The 
wear  and  tear  of  most  of  these  machines  is  great,  due  to  the 
rough  service  under  which  they  usually  operate,  and  also  to  the 
fact  that  the  men  operating  the  machines  do  not  as  a  rule  give 
the  attention  to  lubrication  that  is  really  most  necessary  in  order 
to  prevent  too  frequent  breakdowns. 

The  machines  require  two  different  oils,  one  for  the  gear  case, 
which  should  be  a  heavy  dark  steam  cylinder  oil  which  does  not 
leak  out  easily  from  the  gear  case;  and  another  oil  like  Bearing- 
Oil  No.  5  for  the  motor  bearings  in  electrically-operated  coal 
cutters,  and  for  the  air-operated  engine  in  an  air-operated 
machine. 

The  troublesome  bearings  to  lubricate  are  the  long  sleeve 
surrounding  the  base  of  the  bar  (bar  cutters),  the  vertical  disc 
bearings  (disc  cutters),  and  the  bearings  supporting  the  chain 
wheel  operating  near  the  coal  face  (chain  cutters). 

When  the  long  sleeve  bearing  in  bar  cutters  is  worn,  the  oil 
from  the  gear  case  is  wasted  due  to  leakage.  As  to  the  other 
bearings  mentioned  they  are  exposed  to  coal  dust  and  best  lubri- 
cated by  soft  grease  fed  through  tubes,  so  that  the  bearings  are 
entirely  filled  with  lubricant. 

It  would  seem  as  if  roller  bearings  or  ball  bearings  could  be 
introduced  with  advantage  for  coal  cutters  in  connection  with 
those  bearings  particularly  exposed  to  coal  dust. 

The  percussion  type  of  drill  is  operated  direct  by  compressed 
air  at  high  speed,  1500-3000  blows  per  minute,  requiring  a  thin 
oil  (Pneumatic  Tool  Oil  Light,  page  421),  or  it  may  be  operated 
by  a  pulsator,  as  in  the  Ingersoll  electric  air  rock  drill.  The 
pulsator  is  an  electrically  driven  air  compressor  with  two  cylinders, 
and  no  valves.  The  pistons  force  and  draw  air  alternatively 
to  and  from  the  two  ends  of  the  drill  cylinder;  the  piston  in  the 


LUBRICATION  OF  VARIOUS  WORKS  AND  MACHINERY        535 

drill  cylinder  moves  forwards  and  backwards  and  strikes,  say, 
300  blows  per  minute  on  the  drill  head.  This  machine  requires 
a  more  viscous  oil  like  refrigerator  oil  No.  1,  page  437. 

In  colliery  screening  plants  the  machinery  works  in  a  dusty 
atmosphere.  For  this  reason  ring-oiling  bearings  have  only  been 
a  qualified  success.  The  oil  wells  must  be  cleaned  frequently 
in  order  that  the  oil  may  render  satisfactory  service. 

Oil  syphons  are  easily  choked  by  dust,  but  glass  bottle  needle 
oilers  have  proved  very  reliable  and  satisfactory  in  a  good  many 
cases.  They  are,  however,  liable  to  be  broken  off  or  smashed. 

Lubricating  grease  is  frequently  used  either  through  Stauffer 
screw-down  cups,  or  through  compression  grease  cups,  and  has 
given  good  service  under  a  variety  of  conditions.  The  grease 
fills  up  the  bearing  completely  and  forms  a  protective  fillet  at 
either  end,  which  prevents  the  entrance  of  dust  to  the  bearing 
surface.  There  is  a  marked  tendency  to  introduce  ball  or  roller 
bearings  for  colliery  screening  plants  and  the  like,  preferably 
using  grease  as  a  lubricant. 

MINES  AND  QUARRIES    (EXCLUDING  COLLIERIES) 

It  will  be  unnecessary  to  describe  the  numerous  kinds  of  ma- 
chines installed  in  mines  and  quarries.  Most  of  the  power  units 
are  described  elsewhere,  also  lubrication  of  the  mine  cars.  Steam 
engines  often  operate  with  wet  steam,  requiring  low  viscosity, 
heavily  compounded  cylinder  oils.  This  applies  particularly  to 
small  steam  units,  as  steam  cranes,  steam  rock  drills,  etc. 

One  feature  to  keep  in  mind  with  air  compressors,  gas  and  oil 
engines  is  to  have  the  air  intake  pipes  situated  so  that  only  clean 
air  is  drawn  in,  or  if  the  air  is  full  of  dust,  as  for  example  in  lime- 
stone quarries,  to  provide  suitable  air  filters. 

As  much  of  the  machinery  is  exposed,  low  cold  test  oils  must 
be  used  in  temperate  or  cold  climates,  and  it  is  often  desirable  to 
use  grease  in  place  of  oil  on  bearings  exposed  to  dust  or  grit. 
An  exception  is  the  stonecrusher  bearings,  which  frequently 
employ  grease  and  are  badly  lubricated,  because  grease  is  not 
suitable  for  high  speed  work.  It  is,  however,  difficult  to  fix 
lubricators  in  the  pitman  bearing;  they  usually  shake  off  or 
go  to  pieces  in  a  very  short  time. 

Fig.  204  shows  a  method  which  overcomes  the  difficulty.  A 
bridge  (1)  is  fixed  to  the  stationary  bearings  and  holds  two  sight 
feed  drop  oilers  in  position.  These  oilers  are  connected  by 
flexible  rubber  tubing  (2)  to  the  pitman  head.  Figs.  205  and  206 
show  in  detail  the  tapered  fittings  to  which  the  rubber  tubing 


536 


PRACTICE  OF  LUBRICATION 


is  attached.  The  tubing  has  an  inside  diameter  of  %  inch  and 
an  outside  diameter  of  %  inch. 

As  there  is  a  great  risk  of  pieces  of  stone  being  thrown  about 
by  this  jaw  type  of  crusher  it  is  at  all  times  advisable  to  have 
light  wrought  iron  box-like  covers  made  which  can  be  used  to  slip 
over  the  drop  oilers  to  protect  the  glasses  from  breakage  and  the 
brass  work  from  damage.  Bearing  Oils  Nos.  4  or  5  will  generally 
give  satisfaction. 

In  certain  types  of  pneumatic  stamping  machines  there  is  an 
air  cylinder  interposed  between  the  stamp  and  the  connecting 
rod  which  delivers  the  blow.  The  connecting  rod  takes  hold 
of  the  air  cylinder  and  on  the  down-stroke  compresses  the  air 
above  the  piston  which  is  connected  to  and  actuates  the  stamp. 


Fig.205 


Fig.206 


Fig.204 
FIGS.  204,  205,  206. — Stone  crusher  lubrication. 

When  the  blow  is  delivered  the  compressed  air  acts  like  a  buffer 
and  softens  the  blow.  The  piston  in  the  air  cylinder  must  be 
lubricated  and  owing  to  shocks  and  vibrations,  lubricators  fixed 
on  the  cylinder  generally  shake  off.  One  method  is  to  have 
Stauffer  grease  cups  and  to  stop  the  stamps  now  and  again  to 
give  the  grease  cups  a  turn.  Very  little  lubricant  is,  of  course, 
required.  Grease  is,  however,  a  bad  lubricant  and  output  is  de- 
creased due  to  the  stoppages.  A  viscous  oil  like  Compressor 
Oil  No.  2  (page  416)  is  much  more  efficient,  and  it  can  be  fed 
successfully  by  the  method  indicated  in  Fig.  207.  The  oil  is 
fed  from  the  mechanically  operated  lubricator  (1)  into  the  pipe 
(2)  which  is  telescopically  connected  to  the  pipe  (3).  The  latter 


LUBRICATION  OF  VARIOUS  WORKS  AND  MACHINERY        537 

delivers  the  oil  into  the  air  cylinder,  being  connected  to  a  fitting 
which  allows  it  to  oscillate.  As  the  air  cylinder  moves  up  and 
down,  the  two  telescopic  pipes  oscillate  and  actuate  the  lubricator, 
and  a  sparing  supply  of  oil  is  continuously  and  automatically  de- 
livered to  the  air  cylinder.  Fig.  207  shows  a  two  feed  lubricator 
feeding  two  stamp  cjdinders. 

PAPER  MILLS 

The  exhaust  steam  from  the  main  steam  engines  is  passed  through 
the  drying  rolls  ("dryers")  on  the  paper  machines.     It  is  there- 


FIG.  207. — Mechanical  lubricator  for  stamping  machines. 

fore  important  to  use  good  quality  filtered  cylinder  oils  which  are 
easily  removed  from  the  exhaust  steam,  and  to  use  th em  sparingly . 
If  oil  is  carried  over  to  the  dryers  their  efficiency  is  considerably 
reduced.  Many  paper  mills  could  probably  with  advantage 
mix  oildag  with  their  steam  cylinder  oil  with  a  view  to  reducing 
the  consumption.  All  of  the  exhaust  steam  is  used  for  heating 
purposes,  so  that  even  a  considerable  saving  in  power  iri  a  paper 
mill  by  improved  lubrication  is  not  important  from  a  power 
point  of  view.  The  reduced  qua  tity  of  exhaust  steam  available 
has  to  be  made  up  with  fresh  steam  to  satisfy  the  demand  for 
heating  and  drying  purposes. 

Improved  lubrication  is,  however,  of  great  importance  from 


538  PRACTICE  OF  LUBRICATION 

a  wear  and  t,jear  point  of  view,  which  is  a  considerable  item  in  every 
paper  mill. 

The  paper  machines  at  the  "  wet  end"  have  a  number  of  rollers, 
the  bearings  of  which  get  splashed  with  water.  A  very  soft, 
clinging  grease  should  be  used  for  the  bearings,  or  a  medium 
body  compounded  oil  which  will  "lather"  with  the  water.  Next 
come  the  dryers,  of  which  there  may  be  a  great  number,  say  twenty. 
The  paper,  which  is  delivered  as  a  "wet  carpet"  to  the  first 
dryer,  passes  over  or  under  the  other  dryers  and  becomes  drier 
and  rier,  being  finally  wound  up  on  to  a  large  reel  and  taken 
to  the  calendars  for  finishing  purposes.  The  dryers  have  large 
bearings  placed  in  cast-iron  frames.  The  bearings  become  hot 
due  to  heat  conducted  into  them  from  the  steam,  particularly 
on  that  side  of  the  machine  where  the  steam  enters  through  their 
hollow  journals.  These  large  bearings  are  best  lubricated  by  a 
self-oiling  arrangement,  a  collar  fixed  on  the  journal  dipping  into 
an  oil  well  and  a  stationary  scraper  wiping  the  oil  off  the  collar 
and  guiding  it  into  the  "on"  side  of  the  bearing. 

In  many  of  the  older  paper  machines  plain  bearings  are  em- 
ployed with  the  upper  half  of  the  journal  exposed  and  the  lubri- 
cation is  effected  by  means  of  pieces  of  suet  simply  laid  against 
the  journal.  Suet  is  a  peculiar  lubricant.  It  consists  of  sinewy 
films  with  fatty  matter  interposed  between  the  films.  The 
journal  gets  very  warm  and  grinds  through  a  film,  then  some  fat 
melts  and  greases  the  journal,  until  the  next  film  is  worn  through. 
Although  the  friction  and  wear  are  great,  suet  is  an  exceedingly 
safe  lubricant.  The  journal  never  seems  to  seize  and  the  con- 
sumption of  suet  is  very  low  indeed.  Rancid  suet  causes  pitting 
and  the  lubrication  is  always  very  inefficient. 

Most  bearings  employ  a  high  melting  point,  hard,  fibrous 
grease  in  place  of  suet  and  have  bearing  covers  cast  with  grease 
chambers.  The  best  of  these  greases  are  quite  economical  and 
give  better  lubrication  than  suet,  but  the  wear  is  still  considerable. 
Several  methods  have  therefore  been  devised  to  convert  these 
troublesome  bearings  to  oil  lubrication.  The  difficulty  is  to 
provide  lubricators  which  will  give  a  very  sparing  oil  feed  and 
which  will  stand  rough  usage.  When  the  paper  breaks  on  one 
of  the  dryers,  the  attendant  has  to  hurry,  and  generally  treads 
on  the  bearings  as  he  jumps  about.  Fig.  208  shows  the  Payne 
dryer  box,  consisting  of  an  oil  box  with  hinged  cover,  placed  on 
a  frame  (1)  which  rides  over  the  journal  and  is  fixed  to  the 
lower  bearing  half  (2).  A  felt  pad  (3)  draws  oil  from  the  oil 
box  and  spreads  it  over  the  journal.  The  oil  consumption  can 


LUBRICATION  OF  VARIOUS  WORKS  AND  MACHINERY        539 

be  regulated  to  a  nicety  by  squeezing  the  felt  more  or  less  by 
means  of  the  clamp  (4)  and  adjusting  screw  (5). 

Fitted  with  these  oilers  an  oil  consumption  of,  say,  2J^  gals, 
per  fortnight  for  a  20-roll  machine  (20  dryers,  40  bearings)  can 
be  maintained.  The  lubrication  is  cleaner  and  more  efficient 
than  with  grease,  but  is  not  to  be  compared  with  the  "  collar 
and  wiper"  self  oiling  arrangement  referred  to  on  the  previous 
page.  A  viscous  oil  like  Bearing  Oil  No.  5  should  be  used  for 
both  oiling  systems. 

It  is  quite  customary  and  good  practice  to  hand-oil  sparingly 
grease  lubricated  dryer  bearings,  say,  twice  per  day;  it  improves 
lubrication  and  reduces  wear. 


FIG.  208. — Payne  dryer  box. 

The  calendars  are  similar  to  calendars  used  in  the  textile 
industries  and  require  a  very  viscous  oil  of  great  oiliness,  as 
Bearing  Oil  No.  6,  or  Marine  Engine  Oil  No.l,  or  even  a  Filtered 
Cylinder  Stock,  heavily  compounded  like  Cylinder  Oil  No.  1 
F.H.C.  (page  389).  High  melting  point  fibre  grease  isoccasio  ally 
used,  but  suitable  oil  is  much  to  be  preferred. 

Beater  bearings  are  usually  very  troublesome.  The  pulp  is 
often  thrown  up  into  the  bearings  and  causes  heating  and  scoring. 
Suet  is  probably  as  good  a  lubricant  as  any,  for  the  bearings  as 
now  designed.  It  would  seem  very  desirable  to  design  some 
form  of  grease  filled  bearing,  either  plain  or  roller  type,  which 
would  stand  the  heavy  strain  and  which  by  virtue  of  being 


540  PRACTICE  OF  LUBRICATION 

filled  with  grease  would  be  protected  from  the  entrance  of  pulp, 
etc. 

There  are  usually  a  fair  number  of  small  steam  engine  units 
scattered  about  in  paper  mills,  for  driving  various  machines, 
pumps,  etc.  The  steam  is  generally  wet  and  demands  heavily 
compounded  cylinder  oils.  With  high  speed,  enclosed  engines, 
employing  either  splash  oiling  or  force  feed  circulation,  great 
trouble  is  often  experienced  due  to  an  excessive  amount  of  water 
getting  into  the  oil.  Low  viscosity  circulation  oils  and  a  system 
of  daily  treatment  for  the  oils  is  therefore  essential. 

CEMENT  WORKS 

Some  of  the  most  important  bearings  in  cement  works  are 
the  bearings  for  ball  mills  and  tube  mills  and  for  the  rotary  kiln 
supporting  rollers.  Most  of  these  bearings  receive  a  great  deal 
of  conducted  heat  from  the  kiln  or  from  the  hot  clinker  (ball  or 
tube  grinding  mills).  It  is  good  practice  to  watercool  the  bottom 
halves  of  these  bearings,  so  as  to  facilitate  lubrication.  When 
grinding  mills  are  grinding  cold  material,  the  water  service  is, 
of  course,  not  required. 

The  upper  " halves"  of  the  bearings  are  only  fitted  for  the 
purpose  of  keeping  out  grit  and  dirt  and  to  act  as  receptacles 
for  the  lubricant.  Lubrication  by  means  of  fibre  grease  and  yarn 
grease  is  now  customary  and  quite  satisfactory. 

Jaw  crushers  are  not  often  used  in  cement  works;  their  lubri- 
cation is  similar  to  that  of  stone  breakers  used  in  quarries. 

Cement  works  consume  a  great  deal  of  power;  the  transmission 
drives  are  heavy  and  require  a  viscous  oil  like  Bearing  Oil  No.  5. 
For  electric  motors,  Bearing  Oil  No.  4  should  be  used  as  there 
are  usually  heavy  belt  pulls  to  deal  with. 

A  fair  amount  of  grease  is  generally  used  in  cement  works 
(for  bearings  of  elevators,  conveyors,  etc.,  etc.)  to  prevent  the 
dust  from  entering  the  bearings. 

Pinion  grease  should  be  used  for  the  pinions  and  gears  on 
rotary  kilns,  etc. 

FLOUR  MILLS 

It  has  been  repeatedly  mentioned  that  in  dusty  surroundings 
the  use  of  grease  is  desirable  to  keep  the  dust  out  of  the  bearings. 
In  applying  this  principle  to  modern  flour  mills,  it  must  be  kept 
in  mind  that  much  of  the  machinery  operates  at  high  speeds, 
such  as  the  grinding  machines  (450  to  600  r.p.m.).  Grease  is 
not  suitable  for  high  speed,  except  in  ball  and  roller  bearings;  it 
wastes  a  great  deal  of  power,  so  where  power  is  costly,  grease 


LUBRICATION  OF  VARIOUS  WORKS  AND  MACHINERY         541 

should  not  be  used.  Where  there  is  sufficient  water  power  to 
drive  the  mills  all  the  year  round,  power  saving  is  of  no  importance, 
but  this  is  seldom  the  case,  and  it  should  be  kept  in  mind  that 
suitable  oils  employed  in  place  of  grease  will  save  from  8  per  cent, 
to  10  per  cent,  in  the  full  mill  load.  A  saving  in  power  of  8  per 
cent,  was  obtained  in  one  case  by  replacing  very  viscous  oils 
by  oils  of  the  right  character  and  viscosity. 

Bearing  Oil  No.  4  is  a  good  general  oil  for  flour  mills.  Bearing 
Oil  No.  2  or  3  will  be  preferable  for  the  grinding  machines;  being 
less  viscous  they  will  reduce  the  power  consumption  of  these 
machines  appreciably  as  compared  with  Bearing  Oil  No.  4. 

WOODWORKING  MACHINERY 

For  high  speed  circular  saws  and  planing  machines  Bearing 
Oils  No.  2  or  3  preferably  slightly  compounded,  are  usually  satis- 
factory. 

Heavy  band  saws  require  Bearing  Oil,  No.  4  or  even  Marine 
Engine  Oil  No.  1  when  the  band  pull  is  great.  Marine  Engine 
Oil  No.  1  may  also  be  used  for  chains  and  chainwheels,  as  it 
clings  tenaciously  to  the  surfaces.  For  very  rough  slow  speed 
bearings  and  guides  of  log  machinery,  Black  Oil  is  often  used  and 
is  quite  good  enough. 

Owing  to  the  high  speeds  at  which  most  machines  operate  in 
the  finer  class  of  wood  working  machines,  the  selection  of  the 
correct  grade  of  oil  with  a  reasonably  low  viscosity  will  often 
accomplish  excellent  results  from  a  power  saving  point  of  view, 
and  the  use  of  grease  should  be  confined  to  slow  speed  bearings, 
unless  they  are  ball  or  roller  bearings. 

PRINTING  MACHINERY 

The  important  machines  are  Type  Machines  and  Rotary 
Presses. 

Type  Machines. — For  linotype  machines,  Bearing  Oil  No.  4 
will  prove  satisfactory.  For  monotype  machines,  a  highly  fil- 
tered steam  cylinder  oil,  straight  mineral,  or  slightly  compounded 
with  acidless  tallow  oil  will  prove  efficient.  Unsuitable  oil 
carbonizes  exposed  to  the  great  heat  and  the  type  sticks  together. 

Rotary  Presses. — -These  machines  operate  at  high  speed  and 
are  driven  by  variable  speed  electric  motors.  The  power  con- 
sumption is  an  important  factor  and,  speaking  generally,  most 
presses  employ  oils  far  too  viscous  to  give  the  best  results. 

Savings  in  power  ranging  from  10  per  cent,  to  25  per  cent,  have 


542  PRACTICE  OF  LUBRICATION 

been  accomplished  by  the  introduction  of  Bearing  Oil  No.  2  or  ,'>. 
The  oils  are  preferably  compounded  with  a  non-gumming  oil  like 
good  lard  oil,  as  most  bearings  are  hand  oiled,  but  straight  mineral 
oils  will  also  render  good  service.  For  the  electric  motors, 
Bearing  Oil  No.  2  will  generally  be  found  to  be  the  correct  grade. 

HYDRAULIC  PLANTS 

Apart  from  pumping  engines  in  water  works,  hydraulic  pumps 
are  extensively  used  in  steelworks,  collieries,  many  engineering- 
works,  and  for  hydraulic  elevators,  etc.  All  hydraulic  pumps 
operate  at  slow  speed.  Large  pumping  engines  are  usually 
operated  by  steam,  small  hydraulic  plants  either  by  steam  or 
electric  motors.  Gas  and  Diesel  engines  are  very  occasionally 
used;  they  have  the  disadvantage  that  they  run  at  high  speeds 
and  so  necessitate  a  great  reduction  in  speed,  either  by  two  or 
three  sets  of  reducing  gears  or  by  worm  reduction  gears.  Steam 
engines  are  easily  operated  at  low  speeds  and  drive  the  pumps 
direct. 

Most  hydraulic  pumps  operate  at  very  low  speed  and  pump 
water  against  great  pressure.  These  conditions  call  for  viscous 
oils  with  great  oiliness  for  lubrication  of  cranks  and  main  bearings 
such  as  Bearing  Oils  Nos.  5  and  6  and  Marine  Engine  Oils  Nos. 
1  and  2.  Occasionally  white  greases,  or  other  greases,  rich  in 
animal  oil  or  fat  are  used  and  give  satisfaction  for  very  slow 
speed  work.  Mineral  cup  greases  or  solidified  oils  are  seldom 
suitable,  being  deficient  in  oiliness. 

The  pump  plungers  are  often  difficult  to  lubricate,  particularly 
when  the  stuffing  boxes  are  packed  with  soft  fibrous  packing 
like  hemp  or  flax.  Such  packing  is  usually  soaked  with  tallow 
or  graphite  or  steam  cylinder  oil  and  graphite.  The  addition 
of  graphite  is  very  desirable;  it  helps  to  produce  a  good  surface 
and  prevent  scoring.  Pressure  water,  when  it  leaks  through  the 
stuffing  box  has  an  intense  cutting  action  on  the  plunger  surface, 
and  it  is  the  rule  rather  than  the  exception  to  find  hydraulic 
plungers  scored.  If  the  attendant,  to  stop  a  leak,  screws  the 
packing  up  hard,  intense  friction  is  set  up  in  the  gland,  lubrication 
may  fail  and  the  trouble  is  aggravated.  The  plungers  are  often 
lubricated  externally  by  cylinder  oil  or  grease.  A  compounded 
low  viscosity  cylinder  oil  or  a  mixture  of  lard  oil  and  heavy 
engine  oil  is  quite  suitable,  but  most  greases  increase  the  gland 
friction  enormously;  they  do  not  distribute  themselves  properly 
and  cannot  withstand  the  great  pressure  between  the  plunger 
and  the  packing. 


LUBRICATION  OF  VARIOUS  WORKS  AND  MACHINERY        543 


U.  or  L.  shaped  leather  packing  is  coming  much  into  use  (on 
lines  somewhat  similar  to  the  packing  shown  in  Fig.  171,  page 
428)  and  are  easier  to  lubricate  than  fibrous  packing. 

In  plants  where  the  water,  after  use  in  the  various  hydraulically 
operated  engines,  returns  to  a  main  tank  and  is  circulated  afresh, 
the  ideal  method  of  lubricating  the  plungers  and  valves  in  all 
pumps  and  engines  is  to  make  the  water  carry  the  lubricant. 
This  is  best  done  by  adding  10  per  cent,  of  a  soluble  oil  or 
compound,  which  forms  an  oily  emulsion  with  the  water.  A 
rich  cutting  oil  can  also  be  made  to  emulsify  when  the  requisite 
amount  of  borax  or  soda  is  added  to  the  water  (see  page  573). 
In  plants  where  the  water  is  used  over  and  over  again 
the  introduction  of  soluble 
lubricants  into  the  water, 
where  this  system  has  not 
previously  been  used,  gives 
results  which  are  never  for- 
gotten. 

The  very  long  plungers  in 
hydraulic  elevators  are  also 
efficiently  lubricated  in  this 
manner,  but  when  the  water 
is  run  to  waste  and  therefore 
cannot  be  used  as  a  lubricant, 
the  plunger  must  be  oiled;  an 
oiler  as  shown  in  Fig.  209 
may  be  used.  The  oiler  is 
made  in  two  halves  clamped 
together  around  the  plunger. 
The  oiling  chamber  is  filled 
with  oil-soaked  felt  or  waste, 
and  oil  can  be  applied  through 
a  filling  hole  closed  by  a  screw  plug,  or  by  a  self-closing  ball 
valve. 

Some  hydraulic  plants,  as  for  example  hydraulic  elevators, 
employ  wire  cables  running  over  a  number  of  sheaves.  The 
sheaves  are  lubricated  by  cup  grease  (of  No.  2  or  No.  3  con- 
sistency), as  it  is  not  possible  to  get  near  the  bearings.  Most 
sheaves  have  a  number  of  grease  cups  with  feeding  tubes  going 
to  the  bearings,  so  that  in  any  position  there  is  always  one  grease 
cup  close  at  hand,  which  can  be  given  a  turn.  The  cables  should 
always  be  well  oiled  to  preserve  the  strands  from  corrosion  and 
wear.  Grease  does  not  penetrate  the  cables  and  should  not  be 
used. 


FIG.  209. — Elevator  rod  lubricator. 


544  PRACTICE  OF  LUBRICATION 

GEARS 

Large,  heavy  type  toothed  gearing  as  employed  in  steel  works, 
many  hydraulic  pumping  stations,  cement  works,  etc.,  is  best 
lubricated  by  an  occasional  application—  say  every  four  to  eight 
weeks — of  a  suitable  semi-solid  lubricant.  The  gears  must,  be 
cleaned  before  the  first  application  and  the  grease  should  be 
applied  hot  and  sparingly  by  means  of  a  brush,  so  as  to  form  a 
thin  resilient  coating. 

The  lubricants  most  satisfactory  for  heavy  gear  lubrication  are 
good  quality  pinion  grease  and  exceedingly  viscous,  semi-solid 
petroleum  residues,  similar  to  certain  wire  rope  lubricants.  The 
admixture  of  fine  graphite  is  often  advantageous,  particularly 
with  worn  gears.  Low  viscosity  products  are  unsuitable;  they 
do  not  produce  a  thick  enough  film  to  reduce  noise  and  prevent 
wear. 

High  speed  toothed  gearing  as  employed  in  gear  boxes  of  auto- 
mobiles, motor  trucks,  elevators,  certain  machine  tools,  etc.,  is 
usually  enclosed  in  an  oil  tight  casing  and  is  best  lubricated  by 
oils  of  suitable  viscosity. 

As  most  semi-solid  lubricants  containing  soap  are  inclined  to 
cake  and  cause  trouble,  a  mixture  of  such  lubricants  and  gear 
oil  should  be  resorted  to  only  when  there  is  a  very  great  leakage 
with  gear  oil. 

Worm  gearing  and  worm-wheel  gearing  require  oils  of  great 
oiliness,  owing  to  the  great  pressure  per  square  inch  between  the 
teeth.  The  most  successful  lubricant  for  extreme  conditions  of 
pressure  and  temperature  is  castor  oil.  It  possesses  great  oiliness 
and  an  excellent  cold  test.  For  elevators,  it  is  very  serviceable, 
as  the  worm  gears  are  often  exposed  to  the  cold.  A  mineral  oil 
to  stand  up  to  the  pressures  must  be  of  a  steam  cylinder  oil 
nature  and  compounded  with,  say,  6  per  cent,  to  10  per  cent,  of 
tallow  or  rape,  but  such  oils  have  poor  cold  tests  as  compared 
with  pure  castor.  As  a  result  they  may  be  in  a  congealed  state 
when  the  gear  starts  up  in  the  morning;  they  do  not  therefore 
distribute  themselves  over  the  worm  and  wheel,  and  before  they 
become  liquefied  by  the  frictional  heat,  the  gears  may  have  seized. 

Where  too  low  temperatures  are  not  encountered,  compounded 
steam  cylinder  oils  are  often  preferable,  as  they  do  not  gum  like 
castor  oil.  Dark  cylinder  oils  are  usually  better  than  filtered 
cylinder  oils  as  regards  cold  test.  The  admixture  of  a  small  per- 
centage of  fixed  oil  is  almost  as  effective  as  a  higher  percentage; 
it  greatly  improves  the  oiliness  of  the  mineral  base  and  assists 
in  reducing  friction  and  preserving  the  teeth  from  wear. 


LUBRICATION  OF  VARIOUS  WORKS  AND  MACHINERY        545 


Semi-solid  lubricants  containing  soap  arc  not  so  satisfactory 
as  good  quality  oils,  and  high  melting  point  greases  should  always 
be  avoided,  as  the  worm  or  wheel  simply  pushes  the  grease  to 
one  side  and  it  never  gets  a  chance  to  distribute  itself,  unless 
the  temperature  rises  high  enough  to  rnelt  it. 

As  to  methods  of  application,  there  is  generally  an  oil  well  into 
which  either  the  wheel  or  the  worm  dips,  according  to  their  posi- 
tion relative  to  one  another.  Fig.  210  shows  how  it  is  possible 
to  make  use  of  the  oil  thrown  away  from  the  worm,  by  collecting 
it  in  side  troughs  whence  it  may 
be  guided  to  the  thrust  bear- 
ing and  other  bearings,  finally 
returning  to  the  oil  well. 

CHAINS 

When  chains  are  entirely  en- 
closed in  an  oil  tight  casing, 
they  are  best  lubricated  by  a 
bath  of  oil,  like  Bearing  Oils 
Nos.  4  and  5,  or  oils  of  even 
higher  viscosity,  if  the  casing 
is  not  perfectly  tight. 

Where  chains  operate  ex- 
posed to  dust  and  dirt,  as 
transmission  chains  in  auto- 
mobiles, motor  trucks,  etc.,  it 
is  best  to  remove  them  at  in- 
tervals, clean  them  with  kero- 
sene or  cleaning  oil,  and  afterwards  soak  them  in  a  bath  of  melted 
good  quality  tallow  and  finely  powdered  graphite.  The  tallow 
may  be  replaced  by  a  No.  2  Consistency  Cup  Grease  contain- 
ing a  heavy  viscosity  mineral  oil.  The  solidified  coating  stays 
a  long  time  and  prevents  to  a  large  extent  the  entrance  of  dirt 
and  moisture. 

Lubricating  exposed  chains  by  dropping  oil  on  to  them  before 
or  during  operation  is  wasteful  and  seldom  effective.  Viscous 
oil  is  almost  useless.  When  it  is  not  possible  to  remove  the  chains 
for  soaking  in  lubricant,  as  for  example,  heavy  chains  in  steam 
shovels,  dredging  machinery  and  the  like,  the  lubricant  should  be 
applied  hot  by  means  of  a  brush,  the  same  as  with  heavy  gears. 

ROPES 

Wire  Ropes. — -Most  wire  ropes,  as  used  in  collieries  and  other 
mines,  etc.,  have  a  hemp  core  to  make  them  flexible.  When 

35 


FIG.  210. — Worm  gear  lubrication. 


")46  PRACTICE  OF  LUBRICATION 

ropes  have  to  withstand  severe  heat  or  great  crushing  stresses. 
hemp  cores  are  unsuitable  arid  steel  centres  are  substituted. 

There  are  two  main  types  of  wire  rope,  those  with  ordinary  coil 
construction  and  those  with  locked  coil  construction  (absolutely 
smooth  surface)  as  shown  in  Figs.  211  and  212,  respectively. 

Wire  ropes  deteriorate  with  use,  and  their  life  is  greatly  in- 
fluenced by  lubrication.  If  the  strands  of  the  rope  are  not 
thoroughly  lubricated  or  protected,  moisture  will  penetrate  into 
the  rope  and  cause  rust  and  corrosion.  The  corrosion  may  be 
accelerated  by  galvanic  action,  if  there  be  acid  present  in  the 
water  or  in  the  lubricant.  " Stockholm  Tar"  at  one  time  was  a 
cherished  rope  lubricant,  either  used  alone  or  mixed  with  tallow, 
rosin,  graphite,  etc.  Such  mixtures  are  unsuitable,  as  Stockholm 
tar  and  rosin  contain  acids.  Tallow  also  gets  rancid  and  assists 
in  causing  corrosion.  It  is  very  difficult  to  prevent  corrosion  in 
wire  ropes,  in  which  the  hemp  core  has  become  " chewed  up," 
due  to  the  rope  having  been  subjected  to  excessive  strains. 


FIG.  211. 

Lubrication  of  wire  ropes  is  important,  not  only  to  prevent  cor- 
rosion but  also  to  minimize  the  friction  between  adjacent  strands 
rubbing  against  one  another  when  the  rope  passes  over  pulleys 
or  drums;  a  well  lubricated  ro^pe  in  turn  lubricates  the  sheaves, 
pulleys,  etc.,  over  which  it  passes. 

Too  much  attention  cannot  be  given  to  saturating  the  rope 
with  lubricant  during  manufacture  and  so  giving  it  a  good  start. 
The  hemp  core  should  first  of  all  be  thoroughly  saturated  with 
melted  lubricant  which  afterwards  solidifies.  Before  each  suc- 
cessive layer  of  strands  is  laid  on,  the  rope  must  be  coated  with 
melted  rope  lubricant,  so  that  the  rope  when  leaving  the  manu- 
facturer's works  is  filled  and  saturated  with  lubricants  which 
possess  great  staying  and  moisture-resisting  properties.  It  is 
very  important  that  the  lubricants  be  free  from  acid,  alkali  and 
moisture,  and  free  from  animal  or  vegetable  oils  or  fats,  tar,  rosin, 
filling  matter,  etc.  Otherwise  corrosion  sets  in,  and  if  the  differ- 
ent layers  of  strands  are  not  identical  in  quality  of  steel,  galvanic 
action  takes  place  in  the  presence  of  moisture,  acid  or  alkali, 
and  accelerates  corrosion  of  the  strands. 


LUBRICATION  OF  VARIOUS  WORKS  AND  MACHINERY  .      54? 

The  best  lubricants  for  saturating  wire  ropes,  and  also  for  their 
lubrication,  are  very  viscous  dark  steam  cylinder  oils  or  other 
viscous  petroleum  residues,  either  used  alone  or  mixed  with 
petroleum  jelly  to  solidify  them.  Such  lubricants  can  be  ob- 
tained pure  and  free  from  acid,  alkali  and  moisture,  and  they 
possess  good  lubricating  properties.  They  are  applied  hot.  The 
rope  is  passed  down  through  the  bath  of  liquid  lubricant,  sur- 
plus lubricant  being  squeezed  off,  as  the  rope  leaves  the  bath. 
When  in  use,  the  strands  have  a  tendency  to  force  the  lubricant 
to  the  surface,  so  that  occasional  application  of  rope  lubricant 
is  required,  say,  every  fortnight  under  dry  conditions  and  more 
frequently  under  wet  conditions,  or  when  the  ropes  work  in 


FIG.  213A. 


FIG.  2l'3B. 


Rope  oilers. 


inclined  mine  shafts  or  horizontally  as  the  lubricant  then  gets 
rubbed  off  sooner. 

As  1  o  methods  of  applying  the  lubricant,  hand  greasing  is  still 
largely  used.  The  lubricant  is  applied  by  a  brush,  and  usually 
hot,  so  as  to  give  a  thin  coating.  If  the  rope  gets  dirty  it  should 
be  cleaned  before  applying  the  lubricant.  A  simple  method  is 
to  run  the  rope  through  a  mop  which  removes  loose  dirt  and 
moisture. 

Hand  application  is  now  often  replaced  by  rope  oilers,  as  for 
example,  the  one  shown  in  Fig.  213A.  It  consists  of  a  cast 
casing  (1)  made  in  two  halves,  which  are  hinged  together  and 
clasped  round  the  rope.  The  cup  shaped  portion  of  the  casting 
(2)  is  filled  with  the  lubricant  or  with  sponge  cloth,  thorough!}- 
soaked  with  lubricant.  In  action  the  rope  passes  down  through 
the  oiler.  The  guide  pulleys  (3)  keep  the  rope  central  and  servo 


'548 


PRACTICE  OF  LUBRICATION 


to  distribute  the  lubricant  over  the  rope  surface.  The  oiler  can 
be  used  on  horizontal  ropes,  but  the  cup  (2)  must  then  be  enclosed. 
Some  oilers  have  a  metal  washer,  an  old  rubber  pump  valve 
or  a  piece  of  ordinary  burlap  fitted  round  the  rope  before  it  leaves 
the  oiler,  so  as  to  wipe  off  surplus  lubricant.  Metal  washers  are 
undesirable,  as  with  loose  strands  in  the  rope  (owing  to  wear) 
the  washers  will  strip  the  rope.  Rubber  washers  wear  out  quickly. 
One  pint  of  lubricant  will  suffice  for  coating  100  yards  of  2-in. 
-2J^-in.  rope. 

Quite  a  simple  oiler  is  shown  in  Fig.  213B.  It  consists  of  a 
wooden  cup  made  in  two  halves;  the  cup  is  pushed  into  a  hole 
in  a  plank  which  may  be  fixed  across  the  king 
posts  of  the  winding  head.  A  sponge  cloth  is 
placed  in  the  cup  soaked  with  lubricant.  A 
wooden  cup  will  last  a  long  time  if  made  of  good 
hard  wood  and  will  not  be  torn  by  a  stranded 
rope. 

The  author  is  not  in  favor  of  rope  oilers  which 
employ  saturated  steam  or  compressed  air  for 
atomizing  the  rope  lubricant  and  spraying  it  on 
to  the  rope.  Steam  introduces  moisture  into  the 
lubricant  and  the  rope,  and  it  is  difficult  both 
with  steam  and  compressed  air  to  avoid  waste  of 
lubricant. 

The  lubrication  of  transporter  ropes  of  aerial 
ropeways  is  sometimes  done  by  a  man  being  car- 
ried along  the  rope  and  painting  the  rope,  but  a 
much  simpler  method,  which  saves  labor  and  time, 
is  shown  in  Fig.  214.  One  of  the  rope  pulleys 
running  on  the  transporter  rope  has  both  sides 
FIG.  214. — LU-  covered  in  by  steel  plates,  secured  by  bolts  as 
shown.  The  annular  space  forms  an  oil  reser- 
voir, provided  with  a  filling  plug  through  which 
oil  is  introduced.  The  oil  must  be  just  fluid  enough  at  atmos- 
pheric temperature  to  leak  slowly  through  the  small  hole  or  holes 
provided  in  the  rim,  and  thus  reach  and  lubricate  the  trans- 
porter rope.  Adjustment  is  made  by  plugging  some  of  the 
holes  until  a  suitable  feed  is  attained. 

A  satisfactory  wire  rope  lubricant  must  fulfil  the  same  require- 
ments as  the  lubricants  used  for  saturating  the  rope.  It  must 
remain  soft  and  pliable  under  the  atmospheric  conditions  and 
must  not  be  attacked  by  the  mine  waters  with  which  it  comes 
in  contact  and  which  often  contain  acid  or  chemicals.  It  must 
not  be  thrown  off  or  rubbed  off  too  easily,  yet  it  must  be  suffi- 


LUBRICATION  OF  VARIOUS  WORKS  AND  MACHINERY        549 

ciently  fluid  to  penetrate  through  the  strands  to  the  core  and  so 
keep  the  rope  well  lubricated  internally.  It  must  not  harden  or 
peel  when  exposed  to  cold  and  dirt. 

It  will  be  clear  from  these  remarks  that  very  viscous  or  semi- 
solid  lubricants  of  a  pure  hydrocarbon  character  will  fulfil  these 
conditions.  Thin  oils,  black  car  oils,  or  waste  oil,  are  often  used 
but  are  almost  useless,  as  they  lack  viscosity  and  lubricating 
properties. 

Rope  greases  containing  rosin  soap  or  soap  of  any  kind  or 
filling  matter,  should  not  be  used.  They  do  not  work  their  way 
into  the  rope,  are  inclined  to  cake  and  peel,  and  if  they  contain 
acid,  cause  corrosion. 

Wire  ropes  should  be  examined  daily  by  a  competent  person, 
when  the  condition  as  regards  wear,  lubrication,  etc.,  can  be 
observed. 

Driving  Ropes. — In  the  foregoing,  reference  has  been  made 
only  to  wire  ropes.  The  driving  ropes  employed  for  power 
transmission  are  made  entirely  of  fibrous  material,  such  as  cotton, 
manila  hemp,  etc.,  and  seldom  require  to  be  lubricated,  but  in 
manufacture  they  should  be  more  or  less  soaked  with  a  preserva- 
tive and  lubricant.  A  serviceable  compound  is  made  from  sa- 
ponified tallow,  paraffin  wax  and  graphite.  The  compound  will 
sclidify  and  remain  in  the  rope  during  its  entire  life. 


CHAPTER  XXXII 
OIL  RECOVERY  AND  PURIFICATION 

The  waste  oil  from  bearings  of  steam  engines,  gas  engines, 
large  shaft  bearings,  etc.,  if  collected,  may  often  mean  a  con- 
siderable amount,  particularly  if  reasonable  care  has  been  taken 
to  stop  leakages  by  fitting  efficient  splashguards  and  savealls. 

Such  waste  oil,  if  pure  mineral  or  only  slightly  compounded, 
can  easily  be  made  as  good  as  new  and  used  over  again.  If 
the  oil  is  heavily  compounded,  and  has  been  mixed  with  water, 
only  the  non-emulsified  portion  of  the  oil  can  be  recovered. 
This  is  best  done  by  simple  heating  in  a  settling  chamber,  when 
the  non-emulsified  oil  will  accumulate  at  the  top. 

The  greatest  economy  is  generally  obtained  by  placing  oil 
purifiers — -settling  tanks  or  filters — -in  the  respective  engine 
rooms  or  departments,  and  the  attendant  should  be  made  respon- 
sible for  the  oil  consumption. 

In  the  following  will  be  described  some  of  the  interesting 
aspects  of  oil  purification,  also  a  few  notes  regarding  clarification 
of  oil  charged  with  carbonized  matter,  cylinder  oil  from  exhaust 
steam,  and  the  recovery  of  oil  from  cleaning  materials. 

Oil  Purification. — Purification  of  oil,  whether  it  be  waste  oil 
from  engines  or  machinery  or  oil  in  continuous  circulation,  as  in 
steam  turbines,  consists  of  three  processes,  namely,  Screening. 
Precipitation,  and  Filtration,  provision  for  all  of  which  is  usually 
embodied  in  oil  purifiers,  or  as  they  are  generally  termed,  oil 
filters. 

Screening. — -The  prime  object  of  the  screen  is  to  retain  the 
coarser  impurities  and  relieve  the  filter  section  of  as  much  work 
as  possible. 

Precipitation. — In  the  precipitating  chamber  fine  impurities 
of  higher  specific  gravity  than  the  oil,  such  as  fine  metallic  wear- 
ings  or  water,  are  precipitated.  The  action  is  sometimes  accel- 
erated by  heating  the  oil,  as  the  lower  its  viscosity  the  quicker 
will  the  impurities  separate  out.  Efficient  precipitation  is  very 
desirable  to  enable  the  filter  section  to  operate  for  long  periods 
without  cleaning.  Separated  water  should  be  automatically 
ejected  from  the  system  by  an  automatic  overflow. 

Filtration. — The  object  of  filtration  is  to  remove  the  very 
finest  floating  impurities  in  the  oil  which  cannot  be  retained  by 
the  screen,  or  precipitated  in  the  precipitating  chamber. 

550 


OIL  RECOVERY  AND  PURIFICATION  551 

Filtration  must  not  be  done  by  the  wet  method.  Passing 
dirty  oil  through  water  does  riot  remove  impurities.  The  oil 
rises  through  the  water  in  drops;  the  impurities  are  inside  the 
drops  and  cannot  possibly  be  absorbed  by  the  water,  however 
hot  the  water  may  be.  Dry  filtration  is  the  only  satisfactory 
method. 

In  some  small  oil  filters,  the  oil  is  purified  by  syphoning  from 
the  dirty  oil  compartment  through  woollen  syphons  into  the  clean 
oil  compartment.  Only  clean  and  fairly  dry  oil  will  pass  through 
the  syphons. 

Most  small  filters  employ  cotton  waste,  wood  wool  or  other 
loose  material  as  a  filtering  medium,  but  in  larger  filters,  filter 
cloth  is  now  universally  adopted. 

The  disadvantage  of  loose  material  is  that,  when  this  is  loosely 
packed,  the  oil  passes  through  channels  and  passages  without 
being  filtered.  When  the  filter  material  is  tightly  packed,  the 
capacity  is  very  small,  say  not  more  than  one  or  two  gallons  per 
day.  Even  for  small  filters,  filter  cloth  in  the  form  of  a  simple 
bag  is  preferable  to  loose  filter  material. 

In  Europe  small  filters  are  seldom  made  with  settling'chambers. 
When  the  waste  .oil  is  very  dirty,  it  is  first  treated  in  a  steam 
heated  settling  tank,  and  the  oil,  freed  from  water  and  coarse 
impurities,  is  then  afterwards  treated  in  the  filter. 

Filter  cloth  should  preferably  be  so  arranged  that  the  impurities 
retained  have  a  tendency  to  drop  away  from  the  surface.  With 
horizontal  filter  surfaces  the  oil  should  therefore  pass  upwards. 
Vertical  filter  surfaces  are  more  satisfactory  than  horizontal 
surfaces  with  oil  passing  downwards  through  the  cloth,  as  with 
the  latter  the  dirt  tends  to  clog  the  filter  cloth  more  than  with 
vertical  surfaces. 

It  is  desirable  to  have  the  two  sides  of  the  filtering  surface 
exposed  to  the  same  difference  in  oil  pressure  at  all  points.  If 
the  oil  at  the  bottom  of  a  filter  cloth  is  forced  through  at  greater 
pressure  than  at  the  top,  the  cloth  at  the  top  will  pass  less  oil 
than  the  bottom  portion,  and  on  the  other  hand,  coarse  particles 
may  be  forced  through  at  the  bottom,  unless  the  cloth  is  tightly 
woven. 

When  the  oil  contains  very  fine  impurities,  a  large  area  of  filter 
cloth  is  required,  and  a  slow  flow  of  oil  through  the  filters. 

The  filtering  surface  should  preferably  be  arranged  in  several 
units,  so  that  any  unit  can  be  removed  for  cleaning,  or  be  quickly 
replaced  by  a  clean  filter  unit,  without  interfering  with  the  opera- 
tion of  the  other  units.  Fig.  215  shows  a  No.  5  Peterson  oil 
filter,  made  by  The  Richardson-Phoenix  Co.  The  precipitation 


552 


PRACTICE  OF  LUBRICATION 


chamber  is  illustrated  in  Fig.  216  and  shows  how  water  I'roin  the 
various  trays  passes  to  the  bottom  without  any  danger  of  being 
picked  up  again  by  the  oil.  The  head  (1)  in  the  automatic 
water  overflow  is  adjustable  vertically  to  suit  the  gravity  of  the 
oil.  The  oil  flows  from  the  precipitation  chamber  (Fig.  215) 
through  connection  (1)  into  the  filter  chamber,  passes  through 
the  cloth  in  the  filter  units  to  the  interior  of  each  unit,  and  through 
the  outlets  (2)  into  the  clean  oil  compartment  formed  between 


FIG.  215. — Peterson  oil  purifier. 

and  below  the  precipitation  chamber  and  the  filter  section. 
When  one  of  the  filter  units  is  removed,  its  respective  passage  (2) 
is  automatically  closed  by  a  spring  actuated  valve,  which  is  pushed 
open  when  the  unit  is  again  placed  in  position.  The  pressure 
which  drives  the  oil  through  the  filter  cloth  is  the  same  at  all 
points,  being  equal  to  the  difference  in  height  between  the  oil 
level  in  the  filter  chamber  and  in  the  outlets  (2). 

When  desired,  a  cooling  coil  may  be  fitted  in  the  clean  oil 
compartment.     Such  filters  are  used  as  separate  units  to  deal 


OIL  RECOVERY  AND  PURIFICATION 


553 


with  batches  of  waste  oil  and  also  in  connection  with  gravity 
circulation  oiling  systems  for  steam  engines,  the  whole  of  the 
return  oil  passing  through  the  filter. 

In  steam  turbine  plants,  the  flow  of  oil  is  too  great  to  be  taken 
care  of  by  the  filter,  but  it  is  quite  sufficient  to  by-pass,  say,  5 
per  cent,  of  the  circulating  oil  through  the  filter,  to  maintain 
the  oil  in  the  best  possible  condition. 

Such  firms  as  Richardson-Phoenix  Co.  and  S.  F.  Bowser  &  Co. 
have  done  good  work  in  the  United  States  by  making  manufac- 
turers and  power  plant  owners  realize  the  great  benefits  to  be 


i  — 1 


r 

FIG.  216.  —  Precipitation  chamber. 


derived  from  efficient  circulation  oiling  and  filtration  systems. 
In  this  respect,  Europe  has  something  to  learn  from  the  best 
American  practice. 

Purification  of  Oil  Charged  with  Carbonized  Matter.  —  The 
waste  oil  from  internal  combustion  engines  is  always  dark  because 
of  contamination  with  fine  carbonized  matter,  which  cannot  be 
separated  out  by  filtration.  Gravity  separation  in  large  tanks 
will  in  time  allow  the  oil  to  free  itself,  but  it  means  a  large  volume 
of  waste  oil,  and  the  process  is  very  slow. 

Several  attempts  have  been  made  to  coagulate  the  carbon 
particles,  so  that  they  will  become  large  enough  to  settle  out 
quickly.  A  patented  process,  which  is  reported  to  be  working 
successfully  in  the  United  States,  has  been  adopted  by  the  De  La 
Vergne  Machine  Co.  The  process  consists  in  a  brief  but  violent 


554 


PRACTICE  OF  LUBRICATION 


agitation  of  the  dirty  oil  with  a  solution  of  hot  water  containing 
the  coagulant,  which  is  a  phosphate  of  the  alkali  metals,  as  for 
example,  trisodium  phosphate.  The  action  is  purely  mechanical. 
Within  a  few  hours  after  agitation  all  carbonaceous  matter  is 
precipitated  in  the  form  of  a  layer  of  sludge  between  the  oil  and 
the  water.  It  is  claimed  that  the  oil  is  not  affected  by  the 
coagulant.  Fig.  217  illustrates  one  form  of  this  apparatus. 


OVERFLOW  £D 
FOR  CLtAN  01 


OVERFLOW  EDC 
FOR   WA1EK 


COVER    FOR 
CUTSlOE  TANK 


OVERFLOW 

RINGS 


FAN   Oil 

)UTL£T 

70  STORAGE  TANK 


DRAIN  TO  SEWER 


FIG.    21' 


Synopsis  of  Operation: 

1.  Fill  equal  parts  of  water  and  oil  into  the  inside  tank. 

2.  Heat  the  contents  and  keep  it  hot  during  the  entire  process  by  cir- 

culating hot  water  through  the  outside  tank. 

3.  Dissolve  about  one  pound  of  coagulant  for  each  four  gallons  of  oil  in 

hot  water  and  put  it  in  inside  tank. 

4.  Agitate  thoroughly  for  10  minutes  by  compressed  air,  if  available, 

otherwise  by  mechanical  stirring. 

5.  Let  the  contents  settle  for  about  ten  hours. 

0.  Dra>v  off  the  clean  oil  by  opening  the  communicating  pipe  between  the 
two  tanks.  It  will  overflow  over  the  inside  edge  of  the  top  collar 
at  a  gradually  decreasing  rate.  Adjust  the  height  of  edge  by  adding 


OIL  RECOVERY  AND  PURIFICATION  555 

until  the  overflow  stops  automatically  shortly  before  all  dcMii 
oil  is  drawn  off. 
7.  Drain  the  tank  and  it  will  be  ready  for  the  next  charge. 

Cylinder  Oil  from  Exhaust  Steam. — As  mentioned  elsewhere 
cylinder  oil  in  exhaust  steam  is  usually  present  in  a  more  or  less 
emulsified  condition.  The  oil  skimmed  off  the  hot  well  or  recov- 
ered from  the  exhaust  steam  oil  separator  contains  water,  which 
is  difficult  to  remove. 

A  fair  amount  of  success  has  been  obtained  by  passing  the 
wet  oil  through  a  separator,  similar  to  a  cream  separator.  The 
oil  corresponds  to  the  cream,  the  water  to  the  milk,  and  by  proper 
adjustment,  practically  all  the  oil  can  be  recovered  in  a  reasonably 
dry  condition. 

Recovering  Oil  from  Cleaning  Material. — The  cotton  waste  or 
rags,  sponge  cloths,  mutton  cloths,  etc.,  used  for  wiping  or  clean- 
ing machinery  absorb  a  great  deal  of  oil,  which  can  be  recovered, 
as  well  as  the  cleaning  material,  by  treatment  in  machines  exactly 
similar  to  those  used  for  the  recovery  of  cutting  oils  from  swarf 
and  mentioned  page  566.  The  waste,  cloths,  etc.,  may  be 
washed  in  a  washing  machine  and  dried  on  wire  netting  trays 
in  a  drying  cabinet,  being  then  as  good  as  new.  The  recovered 
oil  is  dirty,  and  must  be  treated  in  a  steam  heated  settling  tank, 
and  afterward  filtered,  before  use.  Unless  it  be  completely 
purified,  it  must  be  used  only  on  rough  machinery. 


CHAPTER  XXXIII 
OIL    STORAGE   AND  DISTRIBUTION 

In  most  plants,  whether  large  or  small,  great  economies  may 
be  secured  by  paying  proper  attention  to  the  system  of  oil 
storage  and  distribution.  In  small  plants  the  oil  is  usually 
stored  in  the  barrels  as  received.  It  is  important,  as  mentioned 
page  69,  that  they  be  stored  under  cover  in  a  dry  place.  The 
barrels  are  placed  on  racks  along  one  side  of  the  room  and  fitted 
with  barrel  taps  for  drawing  off  the  oil.  It  pays  to  have  good 
barrel  taps,  particularly  for  thick  oils  like  cylinder  oil.  The 
taps  should  have  a  large  bore  and  opening  (say  1  in.  to  \Y±  in.) 
and  a  clean  "cut  off/'  so  that  a  minimum  of  dripping  takes  place 
after  the  oil  cans  or  oil  jacks  are  filled.  The  drippings  should 
be  caught  by  drip  pans  and  can  be  used  for  less  important 
machinery  after  accumulated  dirt  and  impurities  are  separated 
out. 

The  practice  of  storing  the  oil  in  the  barrels  is  not  at  all 
satisfactory.  A  great  deal  of  oil  is  often  wasted,  and  if  the  oil 
from  the  drip  pans  is  not  thoroughly  cleaned,  it  may  cause  a 
great  deal  of  trouble.  It  is  better  practice  to  keep  the  oil  in 
cabinets  fitted  with  a  lid,  which  can  be  padlocked,  so  that  no 
unauthorized  person  can  get  access  to  the  oil.  The  cabinets  are 
filled  direct  from  the  oil  barrels.  The  oil  in  the  cabinets  is 
kept  clean.  They  have  a  hand  pump  for  delivering  the  oil  into 
the  oil  cans,  and  surplus  oil  drains  back  through  a  sieve  into  the 
main  reservoir,  so  that  no  oil  is  wasted. 

Such  cabinets  may  also  be  arranged  with  self-measuring  oil 
pumps,  as  supplied  by  S.  F.  Bowser  &  Co.  The  pump  can  be 
adjusted  to  give  a  half -pint,  pint,  or  quart  for  one  full  stroke  of 
the  pump.  An  advantage  of  oil  cabinets  is  that  they  are  practi- 
cally fire  proof.  They  can  be  placed  not  only  in  the  oil  house, 
but  also  in  engine  rooms  or  anywhere  in  the  mill  or  factory  where 
it  is  desired  to  have  an  oil  distributing  unit.  Cabinets  for  depart- 
mental use,  when  empty,  may  be  transported  to  the  oil  house, 
refilled,  and  again  delivered  to  their  respective  departments, 
which  are  then  debited  with  the  amount  of  oil  filled  into  the 
cabinets. 

Another  method  is  to  distribute  oil  in  portable  tanks,  which 
are  filled  in  the  oil  house  and  wheeled  into  the  mill,  and  discharge 
measured  amounts  of  oil  into  the  various  cabinets. 

556 


OIL  STORAGE  AND  DISTRIBUTION  557 

In  larger  plants  padlocked  oil  cabinets  are  impracticable  for 
main  storage  purposes  and  a  row  of  oil  storage  tanks,  usually 
cylindrical,  are  provided  for  the  various  grades  of  oil.  It  is 
good  practice  to  have  the  storage  tanks  so  arranged  that  barrels 
of  oil  can  be  placed  above  them  when  discharging  and  allowed 
to  remain  there  until  properly  drained.  Oil  barrels  may  also 
be  emptied  by  means  of  a  hand  operated  rotary  pump,  or  by 
compressed  air;  but  it  is  difficult  to  empty  them  completely  in 
this  manner,  when  the  oil  is  very  viscous,  as  for  example  heavy 
machinery  oils  or  steam  cylinder  oils. 

The  oil  house  should  preferably  be  at  a  siding  so  as  to  save 
labor  in  delivering  the  oil.  Where  the  consumption  of  one  or 
several  grades  of  oil  is  large  enough  to  justify  installation  of  the 
necessary  storage  capacity,  the  oil  should  be  purchased  in  tank 
cars.  The  price  per  gallon  is  lower  and  the  labor  of  handling 
the  oil  and  the  empty  barrels  is  saved,  as  the  tank  cars  discharge 
straight  into  the  storage  tanks.  Delivery  of  oil  from  storage 
tanks  may  be  done  by  rotary  pumps,  or  compressed  air,  or  by 
self-measuring  pumps.  The  tanks  should  be  fitted  with  tank 
indicators  or  glass  gauges,  showing  the  amount  of  oil  present. 
The  indicators  or  gauges  should  be  graduated  to  show  the  amount 
of  oil  in  gallons,  to  facilitate  stocktaking. 

The  oil  is  delivered  from  the  oil  house  either  in  padlocked 
cabinets  for  departmental  use,  or  in  oil  jacks,  say  %  gal.,  1  gal., 
2  gal.  or  5  gal.  capacity.  The  oil  should  always  be  poured 
through  a  strainer  when' drawn  from  the  storage  tanks. 

The  amount  of  oil  delivered  is  debited  to  the  department 
concerned  and  totalled  up  at  the  end  of  each  month.  A  careful 
entry  must  also  be  made  of  all  supplies,  and  a  check  made  every 
month  to  see  whether  the  stock  at  the  beginning  of  each  month 
plus  supplies  received  minus  total  amounts  delivered  tallies 
with  the  stock  on  hand  at  the  end  of  the  month.  This  will 
frequently  be  found  not  to  be  the  case,  and  the  source  of 
leakage  must  be  immediately  traced  and  rectified. 

Keeping  a  record  of  oil  delivered  does  not,  however,  prevent 
waste  of  oil.  Securing  full  benefit  from  a  proper  storage  and 
distribution  system  can  only  be  done  by  someone,  usually  the 
Chief  Engineer  or  Master  Mechanic,  taking  an  intelligent  interest 
in  the  amount  of  oil  required  for  the  various  units  throughout 
the  works.  Oil  must  never  be  delivered  to  any  department  in 
barrels,  or  other  receptacles  which  are  not  locked.  There  should 
be  a  system  of  daily  or  weekly  allowance  for  each  engine  room 
or  department  and  the  oil  stores  open  only  at  certain  stated 
hours.  The  fixed  allowances  should  not  be  exceeded  by  the 


558  PRACTICE  OF  LUBRICATION 

storekeeper,  except  on  receipt  of  a  special  order,  signed  by  the 
Chief  Engineer. 

Another  system  which  is  equally  efficient,  if  the  Chief  Engineer 
takes  the  necessary  interest  in  it,  is  for  the  Chief  Engineer  on 
his  daily  round  to  give  the  engine  attendants  a  check  in  duplicate 
for  all  oils  required.  The  check  is  given  to  the  storekeeper  and 
the  engine  attendant  retains  the  copy. 

The  Chief  Engineer  should  every  month  scrutinize  the  con- 
sumption sheets  and  revise  the  allowances,  say,  every  three 
months.  Heads  of  departments,  foremen,  overlookers,  etc., 
should  receive  a  copy  of  the  monthly  consumptions,  not  only 
of  their  own  departments,  but  also  of  other  departments,  par- 
ticularly if  the  conditions  are  similar,  as  it  tends  to  create  rivalry 
and  reduce  waste. 

Empty  barrels  should  be  taken  care  of  and  returned  when  a 
sufficient  number  have  accumulated  to  make  a  car  load.  Bar- 
rels which  have  contained  black  oils  are  rated  as  second-class 
barrels,  whereas  barrels  which  have  contained  engine  or  cylinder 
oils  are  rated  as  first-class  barrels,  and  grease  barrels  as  third- 
class  barrels. 

In  works  where  no  organized  system  of  storage  or  distribution 
has  been  in  use,  and  where  some  responsible  person  will  take  an 
intelligent  interest  in  introducing  proper  methods,  including 
regular  allowances  for  every  department,  savings  in  cost  of 
lubrication,  ranging  from  10  per  cent,  to  30  per  cent,  are  often 
obtained,  as  .a  great  deal  of  unnecessary  waste  is  eliminated 
throughout. 

Large  oil  firms  employ  oil  experts  for  the  purpose  of  assisting 
their  customers  in  securing  maximum  economy  of  their  lubricants. 
Most  consumers  will  do  well  to  avail  themselves  of  the  services 
of  such  experts. 


CHAPTER  XXXIV 
CUTTING  LUBRICANTS  AND  COOLANTS 

In  this  section  the  author  has  made  use  freely  of  the  material 
which  he  prepared  for  the  Department  of  Scientific  and  Industrial 
Research,  and  which  was  published  in  1918  in  Bulletin  No.  2 
entitled  "  Memorandum  on  Cutting  Lubricants  and  Cooling- 
Liquids  and  on  Skin  Diseases  produced  by  Lubricants/' 

The  part  dealing  with  skin  diseases  was  prepared  by  Dr.  J.  C. 
Bridge,  H.  M.  Medical  Inspector  of  Factories,  Home  Office, 
and  is  reprinted  in  the  Appendix. 

(1)  Cutting  Lubricants  and  Cooling  Liquids — coolants — are 
oils  or  emulsions  used  in  connection  with  the  cutting  of  metal. 
They   possess  lubricating   and   cooling   properties  in   different 
degrees,  and  the  various  classes  into  which  they  are  divided  may 
be  denned  as  fellows: 

Soluble  Oils.  The  products  known  as  soluble  oils  are  oily  liquids  which 
form  an  emulsion  when  mixed  with  water. 

Soluble  Compounds,  also  known  as  Cutting  Compounds.  Soluble  compounds 
or  cutting  compounds  are  greasy  pastes  which  form  an  emulsion  when 
mixed  with  water. 

Cutting  Emulsions.  Cutting  emulsions  are  aqueous  emulsions  formed 
by  mixing  soluble  oils  or  soluble  compounds  with  water. 

Cutting  Oils.  Cutting  oils  are  oils  such  as  lard  oil,  rape  oil  or  mineral 
oils,  or  a  mixture  of  such  oils  free  from  water  and  from  soap.  These  oils 
do  not  ordinarily  form  emulsions  with  water. 

(2)  Cutting  lubricants  and  coolants  are  used  for  the  purpose 
of: 

(a)  Cooling. 
(6)  Lubrication. 

(c)  To  produce  smooth  finish. 

(d)  To  wash  away  chips. 

(e)  To  protect  the  finished  product  from  rust  or  corrosion. 

(a)  Cooling.  During  operation  the  heat  developed  warms 
not  only  the  tool  but  also  the  material  which  is  being  machined. 
On  cooling  the  latter  will  contract,  and  the  dimensions  will 
differ  from  the  measurements  taken  during  the  process  of  machin- 
ing. The  importance  of  properly  cooling  the  product  is,  therefore, 
obvious,  particularly  under  high-speed  conditions  and  with 
materials,  such  as  aluminium,  which  have  a  high  coefficient  of 
expansion. 

559 


500  PRACTICE  OF  LUBRICATION 

If  the  tool  heats  too  much  the  cutting  edge  will  wear  rapidly. 
The  heat  generated  at  the  point  of  the  tool  is  conducted  into  the 
body  of  the  tool.  If  the  tool  is  of  large  section  the  heat  is  more 
readily  dissipated  than  is  the  case  with  a  tool  of  light  section. 
Efficient  cooling  of  the  tool  edge  reduces  wear  and  enables  a 
greater  output  to  be  obtained.  This  is  most  apparent  with  high 
speed  steel,  the  gain  in  cutting  speed  on  steel  and  wrought  iron 
being  from  30  per  cent,  to  40  per  cent.,  and  on  cast-iron  from 
16  per  cent,  to  20  per  cent.  Efficient  cooling  of  the  shavings 
on  the  side  not  in  contact  with  the  tool  is  particularly  important 
with  tough  material,  as  the  difference  in  temperature  between  the 
two  sides  of  the  shaving  causes  contraction  on  the  cold  side  and 
thus  helps  to  reduce  the  friction  produced  by  the  shavings  rub- 
bing over  the  nose  of  the  tool. 

(b)  Lubrication.    Lubrication   is   of   little   importance  where 
the  machined  article  is  made  of  brittle  material,  as  the  material 
is  removed  in  the  form  of  powder  or  fine  chips. 

Lubrication  is  very  important  where  the  metal  is  tough,  and 
therefore  removed  in  the  form  of  spiral  shavings,  which  grind 
their  way  over  the  nose  of  the  tool.  The  character  of  the  chips 
or  shavings  produced  will  depend  upon  the  form  given  to  the 
tool  by  grinding  and  also  upon  the  angle  at  which  it  is  used. 
The  tougher  the  material  the  greater  will  be  the  metallic  friction 
and  the  greater  the  necessity  for  lubricating  the  nose  of  the  tool; 
otherwise  the  shavings  will  produce  great  friction,  resulting  in 
rapid  destruction  of  the  tool  and  in  rough  finish. 

(c)  To  Produce  Smooth  Finish.     When  the  requirements  of 
cooling  and  lubrication  are  satisfied  the  product  will  receive  a 
good  finish.     Where  a  perfect  finish  is  desired,  experience  has 
shown  that  cutting  oils  possessing  great  oiliness  must  be  applied. 
For  this  reason  various  animal  or  vegetable  oils,  or  rich  mixtures 
of  such  oils  with  mineral  oils,   are  usually  employed.     Some 
engineers  find  vegetable  oils  possessing  great  oiliness,  such  as 
rape  or  cotton  seed  oil,  preferable  to  either  mineral  or  animal 
oils  in  producing  a  very  smooth  finish.     Dies,  taps,  reamers  and 
form  tools  have  a  longer  life  when  used  on  tough  steel  if  a  cutting 
oil  is  employed  in  place  of  an  emulsion  prepared  from  a  compound 
or  soluble  oil.     For  finish  boring,  rifling,  etc.,  a  mixture  of  castor 
oil  and  mineral  cleaning  oil  (gravity  about  .860- .890)  in  the  pro- 
portion of  3  parts  of  cleaning  oil  to  1  of  castor  oil  has  been  used 
with  good  results.     Although  those  oils  do  not  form  a  homogene- 
ous mixture,   the  addition  of  an  equal  volume  of  turpentine 
substitute  (white  spirit)   causes  perfect  solution  to  take  place 


CUTTING  LUBRICANTS  AND  COOLANTS  561 

and  is  said  to  be  advantageous  for  finish-turning  on  guns  and 
other  hard  material. 

For  high  speed  work  it  is  always  desirable  that  the  cutting 
oi)  should  have  sufficient  fluidity  to  ensure  a  rapid  stream  being 
concentrated  where  required. 

(d)  To  Wash  Away  Chips.     Frequently  the  washing  away  of 
chips  is  quite  an  important  function  of  the  cutting  lubricant  or 
cooling  liquid,  particularly  in  cases  of  deep  drilling,  as  in  drilling 
rifle  barrels  and  the  like,  also  in  most  milling  operations. 

If  the  cutting  emulsion  is  used  too  weak  it  will  not  carry  away 
with  it  the  minute  particles  of  metal  and  scale,  which  may  prove 
detrimental  to  the  machine  tool. 

In  the  boring  of  deep  holes,  gun-tubes,  etc.,  a  solution  of  sodium 
carbonate  (50  Ibs.)  and  soft  soap  (25  Ibs.)  in  water  (200  gallons) 
has  been  found  to  give  very  satisfactory  results. 

In  solid  deep-hole  boring,  where  cutting  emulsions  are  used  it 
is  sometimes  found  that  the  emulsion,  in  filtering  through  the 
chips  in  the  bore,  becomes  changed  in  character  in  such  a  manner 
as  to  lose  some  of  its  lubricating  quality. 

In  the  case  of  cast-iron  considerable  advantage  may  be  ob- 
tained by  using  an  aqueous  emulsion  in  order  to  wash  the  dust 
away  from  the  working  parts  and  to  prevent  its  dispersal  in  the 
air. 

(e)  To  Protect  Finished  Product  from   Rust   and   Corrosion. 
Good  cutting  oils  used  "straight"  (i.e.,  not  emulsified  with  water) 
will  not  cause  rusting. 

Cutting  oils  containing  fixed  oils  (animal  or  vegetable  oils) 
such  as  tinged  lard  oil,  with  a  large  percentage  of  free  fatty  acid, 
will  cause  verdigris  on  brass  parts.  Fixed  oils  containing  only  a 
small  percentage  of  free  fatty  acid,  such  as  rape  oil  or  high  quality 
lard  oil,  when  employed,  in  cutting  oils  do  not  produce  verdigris 
unless  the  oils  are  rancid. 

Cutting  emulsions  made  up  from  cutting  compounds  or  solu- 
ble oils  and  water  cause  rusting  if  they  are  used  too  weak,  or  if 
they  contain  acid. 

Emulsions  of  oil  and  water  are  not  stable  in  the  presence  of 
even  minute  quantities  of  acid.  The  acid  causes  separation  of 
the  emulsion  into  layers  of  oil  and  water.  The  water  settling 
out  at  the  bottom  where  the  pump  suction  is  located  is  immedi- 
ately circulated  by  the  pump  and  causes  rusting  of  the  work. 
To  a  limited  extent  the  emulsion  can  be  reformed  by  adding  a 
calculated  quantity  of  ammonia  sufficient  to  neutralize  the  acid, 
but  any  excess  of  alkali  may  facilitate  corrosion  of  the  metal 
being  worked.  Sodium  chloride  (common  salt)  and  other  salts 

36 


5(52  PRACTICE  OF  LUBRICATION 

act  in  much  the  same  way  as  acid,  in  causing  the  emulsion  to 
separate,  only  the  action  is  less  pronounced. 

The  admixture  with  a  soluble  oil  of  kerosene  (5  per  cent,  or 
more)  prior  to  the  addition  of  water  has  been  reported  to  give  good 
results.  A  thin  film  of  kerosene  forms  on  the  top  of  all  standing 
oil  in  barrels  and  tanks  and  prevents  the  access  of  air.  Similarly 
a  thin  film  of  kerosene  forms  over  machined  parts,  machines  and 
tools  which  prevents  gumming  and  rust.  It  should  be  noted, 
however,  that  the  addition  of  kerosene  to  a  soluble  oil  reduces 
its  lubricating  and  emulsifying  properties. 

Emulsions  must  not  be  made  by  mixing  soluble  oils  or  cutting 
compounds  with  hard  water  owing  to  the  precipitate  caused  by 
the  action  of  the  calcium  and  magnesium  salts  in  such  water. 
Soft  water  must  be  used,  which  may  be  either  rain  water  or  dis- 
tilled water,  or  good  quality  town  water,  or  if  only  hard  water  is 
available  it  must  be  boiled  or  softened  by  chemical  means  and 
clarified. 

APPLICATION  OF  CUTTING  LUBRICANTS  AND  COOLANTS 

The  cutting  lubricant  may  be  applied  by  hand-brush  or  oil 
can,  by  drop-feed  from  a  reservoir  fixed  in  a  suitable  position, 
or  it  may  be  circulated  over  and  over  again  by  means  of  a  pump 
operated  by  the  machine  itself,  or  independently  operated, 
serving  a  group  of  machines. 

The  two  first  mentioned  methods  are  only  used  for  slow  speed 
work  where  cooling  of  the  tools  is  of  no  importance.  Practi- 
cally all  modern  machines  require,  however,  before  everything 
else  efficient  cooling  of  the  tools  and  the  cut  articles,  as  without 
such  cooling  the  high  speed  and  'output  made  possible  by  the 
employment  of  high  speed  machine  tools  could  not  be  taken  ad- 
vantage of  to  the  full  extent- 
It-  will  therefore  be  understood  that  what  is  usually  required, 
is  a  large  volume  of  low  viscosity  coolant  (cutting  emulsion  or 
thin  cutting  oil)  delivered  as  near  as  possible  to  the  cutting  edge 
of  the  tool  or  tools  and  delivered  in  a  stream  having  a  low  ve- 
locity— large  cross  sectional  area — so  as  to  avoid  splashing. 
To  deliver  the  coolant  in  a  high  velocity  thin  stream  does  not 
ordinarily  remove  the  heat  effectively  (an  exceptional  case 
where  high  velocity  and  pressure  are  required  being  that  of 
"deep  drilling"  work)  and  it  causes  a  great  deal  of  splashing, 
which  means  a  very  excessive  consumption  of  cutting  oil. 

The  delivery  pipes  should  come  as  close  up  to  the  tool  cutting 
edges  as  possible  (sometimes  flexible  tube  delivery  pipes  are 


5G3 


CUTTING  LUBRICANTS  AND  COOLANTS 


used  with  this  object  in  view)  and  they  should  have  wide 

— flat   bell  mouths — to  reduce  the   velocity    of    the    delivered 

coolant. 

A  simple  device  embodying  this  principle  is  shown  in  Fig.  218. 
On  the  delivery  pipe  (1)  with  closed  end  is  suspended  a  plate 
with  its  lower  edges  bent  together,  leaving  openings,  however, 
for  discharging  the  coolant,  which  is  delivered  from  holes  in 
the  underside  of  the  pipe. 

Great  savings  in  consumption  of  cutting  oil  or  coolants  can 
be  made  in  most  machine  shops  by  paying  attention  to  the  pre- 
vention of  excessive  splashing.  The  loss  of  cutting  oil  depends 
obviously  also  to  a  large  extent  on  the  viscosity  of  the  oil. 


FIG.  218. — Cutting  oil  distributor. 

As  regards  the  type  of  pump  to  be  used  for  circulating  the 
coolant,  plunger  pumps  have  practically  been  discarded  on 
account  of  their  pulsating  discharge.  Rotary  gear  wheel  type 
of  pumps  are  now  more  widely  used  than  the  rotary  vane  pumps 
and  the  centrifugal  pumps.  With  the  two  former  pumps  a 
spring  loaded  relief  valve  must  be  fitted  in  the  discharge  pipe  to 
allow  discharge  back  into  the  reservoir,  when  the  delivery  exits 
are  closed.  Rotary  gear  pumps  are  often  made  so  that  they  will 
deliver  the  coolant  when  running  in  either  direction.  Cen- 
trifugal pumps  are  very  suitable  for  delivering  large  volumes  of 
oil  at  low  pressure  and  are  not  so  easily  choked  as  the  rotary  gear 
or  vane  type  of  pumps. 

When  a  pump  is  not  self  priming  a  non-return  valve  should  be 


564 


PRACTICE  OF  LUBRICATION 


fitted  on  the  suction  side,  or  the  pump  should  pref.ernblu  bo  sub- 
merged in  the  reservoir. 

It  is  good  practice  to  have  a  large  volume  of  coolant  in  the  cir- 
culation system,  as  it  helps  to  dissipate  the  heat  and  the  coolant 
therefore  keeps  cooler. 

When  a  group  of  machines  are  engaged  on  similar  work  or  their 
cutting  oil  requirements  are  practically  identical,  they  may  with 
advantage  be  supplied  from  a  common  circulation  system,  with 
discharge  pipes  distributing  the  oil  through  branch  pipes  to  each 
machine,  the  return  oil  passing  through  return  pipes  to  a  central 
tank,  whence  the  oil  is  circulated  afresh.  Group  systems  with 
central  tanks  are  excellent  where  one  mixture  is  used  on  all  ma- 
chines on  the  circuit. 

Return  pipes  should  be  large  and  should  be  arranged  for  easy 
access  for  cleaning.  In  large  systems  isolating  valves  should  be 


Qi 

FIG.  219.— -Cutting  oil  circulation. 

employed  to  sectionize  the  system.  Efficient  strainers  should 
be  fitted  on  all  return  pipes  and  pump  sections  and  should  be 
cleaned  daily.  Tanks  as  a  rule  should  be  cleaned  out  every 
6  weeks  and  return  pipes  every  6  months.  Any  scum  formed 
should  be  skimmed  off  the  tanks  daily. 

It  is  important  both  with  this  system  and  where  machine 
tools  have  individual  pumps  that  the  pump's  suction  should  be 
always  covered  so  that  air  cannot  be  drawn  into  circulation, 
since  aeration  of  the  circulating  medium  has  a  strong  oxidizing 
effect  upon  the  oil  or  emulsion. 

When,  however,  the  machine  tools  or  the  kinds  of  work  done 
are  of  a  varied  character,  it  is  necessary,  when  a  circulation  sys- 
tem is  employed,  to  be  able  to  cut  out  certain  machines  from  the 
general  supply  so  that  they  may  use  a  separate  quality  of  cutting 
oil  or  coolant  and  have  their  circulation  system  self-contained. 
Fig.  219  is  a  diagram  illustrating  a  supply  system  by  Richardson- 


CUTTING  LUBRICANTS  AND  COOLANTS  565 

Phoenix  Co.  of  Milwaukee,  Wis.,  U.  S.  A.,  which  embodies  this 
feature.  The  cutting  oil  is  discharged  from  the  1^-in.  delivery 
main  (1)  through  %-m.  branch  pipes  (2)  and  a  %-in.  service 
pipe  (3)  controlled  by  a  gate  valve  (4) .  The  used  oil  is  lifted  by 
a  rotary  pump  (5)  from  the  base  chamber  into  the  %-in.  return 
branch  pipe  (6)  fitted  with  gate  valves  (4)  and  check  valves  (7) , 
delivering  the  oil  either  into  the  3-in.  steelwork  return  main  (8) 
or  the  3-in.  brass  work  return  main  (9),  there  being  separate 
return  mains  and  filtration  tanks  for  the  oil  coming  from  the 
steel  work  and  brass  work  section  respectively. 

When  a  machine  is  cut  out  from  the  circulation  system,  the 
rotary  pump  circulates  the  oil  through  the  %  in.  service  pipe 
(10),  the  service  pipe  (3)  being  shut  off  by  the  gate  valve  (4). 
In  America  such  systems  are  generally  used  and  their  design 
may  of  course  be  adapted  to  the  particular  requirements  of  large 
machine  shops.  It  deserves  to  be  mentioned  that  filtration  and 
sterilization  of  the  return  oil  are  features  of  many  large  plants. 
The  filters  are  very  much  of  the  designs  mentioned,  page  552,  but 
in  addition  chambers  heated  by  steam  coils  sterilize  the  oil,  heat- 
ing it  to  about  200°F.  and  the  oil  returned  from  the  steelwork 
section  passes  a  magnetic  separator,  which  is  very  effective  in 
removing  steel  and  iron  particles,  but  naturally  has  no  effect 
on  brass,  aluminum  or  other  non-magnetic  metallic  particles. 
The  iron  and  steel  chips  adhering  to  the  magnet  may  be  automat- 
ically removed  by  scrapers  fitted  to  an  endless  chain  which 
travels  over  the  surface  of  the  magnet,  the  chips  dropping  into 
a  receiving  vessel  at  the  side. 

Although  filtration  even  through  finely  woven  cloth  will  not 
remove  the  very  finest  particles,  yet  well  filtered  oil  appears  to 
be  quite  satisfactory  without  the  need  of  long  time  separation 
by  gravity  in  steam  heated  settling  chambers. 

RECLAIMING  OIL  FROM  SWARF 

The  consumption  of  cutting  oil  is  made  up  of  various  losses, 
principally  those  due  to  oil  splashing  away  from  the  machines, 
as  already  mentioned,  and  oil  adhering  to  the  swarf  chips  and 
turnings. 

In  the  case  of  cutting  emulsions  the  swarf  drains  fairly  clean 
by  gravity  alone,  but  when  cutting  oils,  particularly  if  they  are 
viscous,  like  lard  oil,  are  used  straight,  a  large  amount  adheres  to 
the  swarf.  From  50  per  cent,  to  80  per  cent,  of  the  daily 
consumption  can  be  saved  by  reclaiming  cutting  oil  from  the 
swarf  in^separators  operating  at  high  speed,  the  peripheral  speed 
being  as  high  as  6000-7000  feet  per  minute,  Fig.  220 illustrates  a 


5(50 


PRACTICE  OF  LUBRICATION 


turbine  driven  machine;  smaller  machines  are  mostly  belt  driven. 
The  turbine  is  of  the  de  Laval  type.  The  steam  has  a  slight 
emulsifying  effect  on  compounded  cutting  oils,  so  that  in  this 
respect  belt  driven  machines  are  preferable.  When  removing  oil 


FIG.  220. — Separator 
for  oil  recovery. 

1.  Steam  nozzle. 

2.  Revolving 

cage. 

3.  Perforations  in 

the  dome  ad- 
mitting steam 
to  cage;  use- 
ful when  re- 
moving  oil 
from  waste. 

4.  Exterior      sta- 

tionary cham- 
ber. 

5.  Syphon  for  oil 

discharge. 


from  wiping  materials  (for  which  these  separators  are  also  used), 
the  presence  of  steam  helps  to  liquefy  the  oil  and  thus  separate 
it  more  completely  from  the  wiping  material,  the  recovery  of 
which  is  the  prime  object. 


FIG.  221. — Spratts  oil  purifier. 

1.  Dirty  oil  receptacle. 

2.  Oil  feed  into  revolving  cage. 

3.  Revolving  cage. 

4.  Water. 

5.  Outer,  stationary  chamber. 

6.  Purified  oil  receptacle. 

7.  Belt  drive. 


Steam  of  20  to  40  Ibs.  pressure  is  generally  employed.  The 
wiping  material  is  afterwards  washed  and  dried,  The  clean 
swarf  is  remelted  on  the  works  or  sold. 


CUTTING  LUBRICANTS  AND  COOLANTS  567 

The  reclaimed  oil  is  dirty,  containing  fine  metallic  particles 
in  suspension  and  must  be  further  purified  by  heating  in  large 
settling  tanks  where  the  metallic  impurities  and  emulsified  oil 
separate  out  by  gravity  alone,  or  the  oil  must  be  well  filtered. 
The  oil  cannot  very  well  be  completely  purified  by  separators, 
as  the  very  finest  particles  float  like  fine  dust  in  the  oil  and  take  a 
long  time  to  separate  out. 

Spratt's  separator  used  for  purifying  oil  is  shown  in  Fig.  221. 

Sufficient  water  (4)  is  first  of  all  poured  into  the  cage  (3)  to 
form  a  vertical  cylindrical  wall,  when  the  cage  revolves.  The 
oil  rises  in  a  thin  film  up  this  wall  and  is  thrown  out  at  the  top, 
whilst  the  heavy  impurities  leave  the  oil  film,  dive  through  the 
water  and  collect  on  the  inside  of  the  cage,  whence  they  can  be 
removed  'at  intervals. 

SELECTION  OF  CUTTING  LUBRICANTS 

Before  selecting  the  correct  grade  of  cutting  lubricants  it  is 
necessary  to  consider  several  important  factors  such  as : 

(a)  Cutting  speed  and  depth  of  cut. 

(b)  The  material  under  manufacture. 

(c)  The  system  of  application  of  the  lubricant  or  emulsion, 
(rf)  The  production  of  skin  diseases.     (See  page  600.) 

(a)  Cutting  Speed  and  Depth  of  Cut. 

Low  Speed  and  Shallow  Cut.  Low  speed  and  shallow  cut 
require  little  cooling  and  little  lubrication. 

Low  Speed  and  Heavy  Cut.  Low  speed  and  heavy  cut  parti- 
cularly if  the  material  is  tough,  demand  a  cutting  lubricant 
possessing  great  oiliness. 

High  Speed  and  Shallow  Cut. — High  speed  and  shallow  cut 
demand  a  cutting  medium  with  great  cooling  properties,  conse- 
quently emulsions  are  frequently  used.  Where  a  perfect  finish 
is  desired,  low  viscosity  cutting  oils  are  used  "straight." 

Where  the  speeds  are  particularly  high  emulsions  only  should 
be  used,  as  otherwise  there  will  be  excessive  heating  of  the  tools 
and  of  the  product.  A  mixture  of  kerosene  with  lard  oil  or  other 
cutting  oil  for  high  speed  work  in  connection  with  aluminium  has 
given  good  results  but  is  somewhat  dangerous  and  has  led  to 
several  fires.  It  is  perhaps  better  to  use  cutting  emulsions  which 
possess  the  necessary  cooling  properties  and  are  not  inflammable. 

High  Speed  and  Heavy  Cut. — High  speed  and  heavy  cut  de- 
mand a  cutting  lubricant  with  great  cooling  as  well  as  lubricating 
properties,  so  that  heavily  compounded  cutting  lubricants  of  low 
viscosity  must  be  used.  Low  viscosity  is  necessary  to  give]  good 


568  PRACTICE  OF  LUBRICATION 

cooling  effect,  and  heavy  compounding  with  animal  or  vegetable 
oils  is  requisite  so  as  to  lubricate  the  tools  and  shavings  effect- 
ively and  prevent  wear  as  far  as  possible.  A  rich  emulsion  pro- 
duced from  an  oil  containing  a  high  percentage  of  vegetable  oil 
has  also  proved  satisfactory,  as  the  excellent  cooling  properties 
of  the  rich  emulsion  compensate  for  its  lower  degree  of  oiliness  as 
compared  with  heavily  compounded  cutting  oils  used  straight. 

(b)  Material  under  Manufacture.  The  influence  of  the  mate- 
rial upon  the  choice  of  cutting  oil  has  already  been  referred  to. 

Where  material  is  brittle,  cutting  emulsions  are  nearly  always 
used,  as  very  little  lubrication  is  required.  When  cutting  oils 
are  used,  there  will  be  no  need  for  any  compounding  with  fixed 
oil,  so  that  straight  mineral  oils  may  be  employed. 

The  amount  of  soluble  oil  or  soluble  compound  used  for  pre- 
paring the  cutting  emulsion  varies  from  2J^  per  cent,  to  20  per 
cent.,  the  richer  mixtures  being  used  for  severe  conditions,  and 
the  weaker  mixtures  for  light  duties  or  for  materials  such  as 
brass  and  aluminium  where  there  is  no  danger  of  rusting. 

Where  the  material  is  tough,  but  the  speeds  are  high  and 
the  cut  not  too  heavy  cutting  emulsions  are  also  frequently 
employed;  but  where  the  material  is  tough  and  the  cut  medium 
•or  heavy,  it  is  often  preferable  to  employ  cutting  lubricants 
used  " straight"  and  containing  a  percentage  of  animal  or  vege- 
table oils  (ranging  from  10  to  50  per  cent.)  or  consisting  entirely 
of  such  oils  (see  also  remarks  in  previous  paragraph). 

Straight  mineral  oils  may  have  to  be  used  with  tough  material 
and  light  or  medium  cutting,  if  the  oil  is  particularly  exposed 
to  oxidation,  as  for  example  in  the  Gridley  Automatics,  which  are 
designed  for  very  rapid  production  and  therefore  also  "punish" 
the  oil  much  more  than  most  other  machines.  The  oil  is  in 
rapid  circulation,  gets  mixed  with  air  and  exposed  to  heat  when 
touching  the  tools  or  the  articles — in  other  words,  the  oil  is 
exposed  to  the  strong  oxidizing  effect  of  heat  and  air.  Any 
admixture  of  fixed  oil  may  under  these  conditions  produce 
gumminess  and  semi-carbonized  deposits,  whereas  with  pale, 
well  refined  mineral  oils  the  system  will  keep  clean  and  free 
from  troublesome  deposits. 

The  absence  of  fixed  oil  means  less  oiliness  of  the  cutting  oil, 
so  that  the  tools  will  wear  more  and  have  to  be  reground  more 
frequently. 

Cutting  oils  or  emulsions  are  sometimes  affected  by  small 
percentages  of  acid  or  alkali,  etc.,  introduced  into  the  oil  in 
circulation  by  the  swarf  from  materials  such  as  galvanized 
fittings,  pickled  castings  or  forgings,  etc. 


CUTTING  LUBRICANTS  AND  COOLANTS  569 

(c)  System  of  Application.-  -  The  iin  purl-ant  point  to  keep  in  mind 
in  regard  tu  the  system  of  application  is  that  where  the  uil  or  the 
emulsions  are  circulated  over  and  over  again,  they  are  exposed 
to  the  oxidizing  effect  of  air  and  to  admixture  with  dust  and  dirt 
from  the  machine  shop,  and  oils  should  be  selected  which  will 
withstand  this  effect  without  gumming  or  carbonizing  too  much. 

When  the  oil  is  not  circulated  but  used  once  only,  it  need  not 
possess  non-gumming  properties. 

The  bearings  and  slides  of  machine  tools  should  be  protected 
as  far  as  possible  from  the  spray  of  cutting  oil  or  emulsion,  as 
they  will  often  be  inclined  to  gum,  corrode  or  rust  and  thus 
cause  trouble  with  lubrication.  Many  cutting  emulsions, 
cutting  oils  containing  vegetable  oils,  and  those  containing  very 
poor  animal  oils  (high  acidity)  are  the  worst  offenders.  Cutting 
oils  containing  non-drying  fixed  oil,  low  in  acid  contents,  do  not 
give  any  trouble  if  they  get  mixed  with  the  lubricating  oil  in  the 
bearings  or  on  the  slides. 

COMPOSITION  AND  CHARACTERISTICS  OF  CUTTING  OILS, 
SOLUBLE  OILS  AND  COMPOUNDS 

Cutting  Oils. — The  mineral  oils  which  are  best  suited  to  be 
used  as  cutting  lubricants,  either  alone  or  mixed  with  animal 
or  vegetable  oil,  are  pale  in  color  and  of  low  viscosity,  ranging 
from  100  in.  to  200  sees.  Saybolt  at  104°F.  The  lower  viscosity 
oils  must  be  used  for  high  speed  conditions,  and  oils  with  higher 
viscosity  may  be  used  for  slow  speed  conditions. 

The  oils  must  not  be  lower  in  viscosity  than  indicated,  because 
they  will  then  be  too  volatile;  a  large  proportion  will  vaporize 
exposed  to  the  heat  at  the  tool  edge  and  create  smoke  and  fumes 
which  are  very  objectionable.  With  cutting  emulsions  steam 
only  is  produced. 

Of  the  animal  oils  used  either  alone  or  in  admixture,  tinged 
lard  oil  containing  as  much  as  10  per  cent,  to  15  per  cent,  of 
free  fatty  acid  is  often  used.  Whale  oil  is  also  frequently  em- 
ployed, but  under  severe  conditions  these  oils  are  inclined  to 
gum  and  a  better  quality  lard  oil  must  be  used,  with  a  low 
acid  contents,  say  below  6  per  cent.  Such  lard  oils — Prime 
lard,  Extra  No.  1  lard  (they  go  under  different  names) — are  of 
course  more  expensive. 

All  lard  oils  congeal  in  cold  weather  and  always  cause  a  certain 
amount  of  gumming,  so  that,  wherever  possible,  a  mixture  of 
lard  oil  and  low  cold  test  mineral  oil  is  to  be  preferred  on  account 
of  its  greater  fluidity  in  the  cold  and  less  tendency  to  gum. 


570  PRACTICE  OF  LUBRICATION 

Cutting  oils  containing  vegetable  oils,  particularly  it  they,  arc 
heavily  blown  (i.e.,  thickened  by  oxidation)  are  liable  to  produce 
gummy  deposits  in  circulation  systems  of  individual  machines 
or  in  the  pipe  systems  serving  a  group  of  machines.  These 
deposits  interfere  with  the  proper  operation  of  the  machines  and 
necessitate  frequent  cleaning,  which  not  only  increases  the  costs, 
but  also  decreases  the  output. 

Cotton  seed  oil  oxidizes  more  readily  than  rape  oil,  and  should 
never  be  used  in  the  manufacture  of  cutting  lubricants  that  are 
to  be  used  in  a  circulation  system. 

Animal  oils  on  the  whole  are  not  so  easily  oxidized  in  a  cir- 
culation system  as  are  vegetable  oils  and  should  therefore  be 
preferred  unless  the  oil  is  used  only  once  and  not  circulated. 

Cutting  oils  are  nearly  always  used  " straight,"  i.e.,  without 
admixture  of  water.  Certain  cutting  oils,  however,  containing 
at  least  5  per  cent,  of  free  fatty  acid  and  preferably  at  least  25 
per  cent,  of  saponifiable  oil  (animal  or  vegetable  oil)  may  either 
be  used  " straight"  or  in  the  form  of  cutting  emulsions.  They 
will  emulsify  with  water  to  which  the  requisite  amount  of  alkali 
(soda  ash,  borax,  etc.)  has  been  added.  An  excess  of  alkali 
causes  rapid  wearing  away  of  the  tool  edge  and  must  therefore 
be  avoided. 

NOTE. — When  the  cutting  oil  has  been  sterilized  by  the  addition  of  say 
1  per  cent,  carbolic  acid  and  is  also  used  for  lubrication,  it  occasionally  gives 
trouble,  as  for  example  in  the  case  of  some  clutches  in  automatic  machines, 
having  a  very  short  movement,  about  KG  in.  They  were  oiled  when  the 
clutch  was  put  together  and  then  expected  to  do  without  lubrication  for 
many  months.  The  effect  of  the  carbolic  acid  in  the  stagnant  oil  was  to 
absorb  moisture  from  the  air  and  cause  the  clutches  to  rust  and  stick. 

GRADES  OF  CUTTING  OILS 

Before  giving  specific  recommendations  for  cutting  oils  a  few 
remarks  may  prove  useful  on  the  subjects  of  viscosity,  compound- 
ing, color,  oxidation,  etc. 

High  viscosity  mineral  oil  has  slightly  more  oiliness  than  low 
viscosit}'  mineral  oil,  but  if  great  oiliness  is  required  it  is  better 
to  mix  a  percentage  of  fixed  oil  with  low  viscosity  mineral  oil, 
rather  than  use  a  higher  viscosity  oil.  When  a  straight  mineral 
oil  with  a  maximum  oiliness  is  required  then,  of  course,  the  only 
thing  to  do  is  to  use  as  high  a  viscosity  oil  as  the  cooling  require- 
ments will  permit.  High  viscosity  means  that  less  oil  spray 
will  be  formed,  therefore  less  oil  wasted  by  splashing  (or  leakage) . 

High  viscosity  in  a  cutting  oil,  speaking  generally,  is,  however, 
undesirable,  as  the  oil  is  inclined  to  hold  metal  chips  in  suspension. 


CUTTING  LUBRICANTS  AND  COOLANTS  571 

It  adheres  in  great  quantities  to  the  swarf  and  is  difficult  to 
remove.  High  viscosity  also  means  diminished  cooling  prop- 
erties. The  rapidity  with  which  the  oil  removes  heat  and 
radiates  the  absorbed  heat  afterwards  is  probably  in  direct 
proportion  to  the  fluidity  of  the  oil. 

Low  viscosity  is  nearly  always  desirable.  The  oil  does  not 
hold  metal  chips  in  suspension,  but  is  easily  clarified  by  gravity 
or  by  nitration.  Comparatively  little  oil  adheres  to  the  swarf 
and  is  easily  removed  in  the  separator.  Low  viscosity  is  de- 
manded, when  the  oil  must  have  good  cooling  properties. 

Low  viscosity  oil  is  particularly  required  for  aluminium,  as 
otherwise  the  aluminium  dust  floats  and  settles  out  only  with 
great  difficulty.  A  mixture  of  50  per  cent,  cutting  oil  (more 
or  less  compounded)  +50  per  cent,  kerosene  has  given  good 
results  for  aluminium — also  cutting  emulsions,  which  have 
even  lower  viscosities. 

Compounding. — A  high  percentage  of  compound  gives  the  oil 
great  oiliness  and  is  therefore  required  where  good  lubricating 
properties  are  needed,  i.e.,  for  severe  cutting  in  tough  material 
and  particularly  where  a  perfect  "finish"  is  required,  which 
cannot  be  accomplished  unless  the  chips  move  away  smoothly 
over  the  well  lubricated  tool  face. 

The  most  exact  requirement  as  regards  " finish,"  such  as 
reaming  and  rifling  of  rifle  barrels,  can  only  be  met  by  using 
pure  animal  or  vegetable  oils,  such  as  lard  oil,  sperm  oil  or  olive 
oil. 

Where  the  finishing  cut  on  hard  materials  is  very  fine,  mixtures 
of  fixed  oils  with  kerosene  have  given  good  results,  such  as  50 
per  cent,  lard  oil  and  50  per  cent,  kerosene,  or  12.5  per  cent, 
castor  H-  37.5  per  cent,  cleaning  oil  (.860-.890)  +  50  per  cent, 
turpentine  substitute  (.760-.780),  etc. 

Color  and  Acid. — As  cutting  oils  used  in  circulation  systems 
are  exposed  to  heat  and  the  oxidizing  action  of  air,  pale  colored 
oils  should  always  be  preferred,  as  they  produce  less  carbon  than 
dark  colored  oils,  and  therefore  give  cleaner  results. 

It  has  already  been  indicated  that  tinged  lard  oil,  when  it  is 
excessively  acid  (and  dark  in  color)  is  more  easily  decomposed 
and  leads  to  the  formation  of  gummy  dark  deposits,  wrrreas 
pale  colored  lard  oil  low  in  acid  contents,  say  below  6  per 
cent.,  is  rather  free  from  this  objection. 

Other  chemical  or  physical  tests  are  of  little  use  in  judging 
cutting  oils,  except  in  so  far  as  they  disclose  characteristics  of 
the  oils  which  would  condemn  them  from  a  general  quality  point 
of  view,  such  as  presence  of  moisture,  glue,  dirt  and  impurities. 


572 


PRACTICE  OF  LUBRICATION 


etc.  It  is,  however,  conceivable  that  some  kind  of  oxidation 
test  by  blowing  air  through  the  heated  oil  (see  page  590)  may 
prove  useful  in  comparing  the  gumming  tendency  of  different  oils. 

The  open  flash  point,  as  long  as  it  is  above  300°F.  need  not  be 
considered.  Of  course,  mixtures  with  kerosene  and  turpentine 
substitute  have  very  low  flash  points  and  precautions  must  be 
taken  to  minimize  the  risk  of  fires. 

In  Table  32  is  given  a  fairly  complete  line  of  cutting  oils, 
together  with  a  rough  guide  as  to  their  uses. 

TABLE  No.  32 


Cut- 

""f 

Per  cent, 
of  com- 
pound 

Nature  of 
compound 

Saybolt 
viscosity 
at  104°F., 
min. 

Acidity  in 
terms  of 
oleic  acid, 
per  cent. 

Recommended  for 

Speed 

Cutting 

Material 

'No.  1 
No.  2 
No.  3 


Cottonseed     or     160-200     Below     6   Slow 


Heavy 


Tough 


Extra     No.      1  100-120   j  Below     3|  High  Medium  and   Tough 

lard  heavy 

15  per  cent,  ex-  120-140     Below     2   Moderate   Medium  and;  Tough 

tra  No.  1  lard;  to      high    heavy 

15      per     cent. 

tinged  lard 


No.  4       12.5        Tinged  lard  or    120-140   j  Below  1.5   Moderate 

to      high 


Light      and      Tough 
medium 


.  5 


).  7! 


Nil 
Nil 


No.       1      pale 
whale 

Tinged  lard  or    100-120     Below  1.0   Moderate!  Light  Tough  or 

No.       1       pale  to      high  brittle 

whale 

100-120   !        Nil          Moderatej  Light  or   Brittle 

to      high     medium 

160-200  Nil          Moderate!  Medium      or   Brittle 

to      high    heavy 


1  No.  1  Cutting  oil  must  not  be  used  in  circulation  systems. 

2  Nos.  6  and  7  are  also  recommended  for  cutting  tough  and  hard  material  in  machines,  such 
as  the  Gridley  automatics  in  which  compounded  oils  are  particularly  inclined  to  gum  and 
carbonize. 

Pure  lard  oil  or  sperm  oil  is  recommended  for  reaming  and 
rifling  rifle  barrels  or  similar  operations  on  tough  material,  where 
a  perfect  finish  is  imperative,  when  the  " Finishing  Cut"  (usually 
a  very  fine  one)  is  taken. 

Sperm  oil  is  a  better  coolant  than  lard  oil  on  account  of  its  low 
viscosity,  but  is  not  quite  so  "oily"  as  lard  oil. 

A  mixture  of  50  per  cent,  lard  oil  and  50  per  cent,  kerosene  is 
recommended  for  the  finishing  cut  on  guns  or  other  hard 
material;  it  can  also  be  used,  but  is  usually  unnecessarily 
expensive,  for  cutting  aluminium. 

A  mixture  of  50  per  cent,  cutting  oil  No.  3  +  and  50  per  cent. 
kerosene  is  recommended  for  cutting  aluminium,  but  the  danger 
of  fire  must  not  be  overlooked. 


CUTTING  LUBRICANTS  AND  COOLANTS  573 

SOLUBLE  OILS  AND  COMPOUNDS 

Soluble  oils  are  prepared  by  dissolving  a  soap  (usually  less  than 
20  per  cent.)  in  a  mixture  of  mineral  oil  (usually  less  than  70  per 
cent.)  and  saponifiable  oil  (usually  more  than  15  per  cent.). 

The  saponifiable  oils  used  in  making  the  soap  are  of  either 
animal  or  vegetable  origin  such  as  lard  oil  or  other  olein  from 
animal  fat,  linseed  oleic  acid,  light  wool  grease,  castor  oil,  sul- 
phonated  or  hydrolyzed  castor  oil,  rape  oil,  cotton  seed  oil, 
rosin,  rosin  oil,  etc.,  and  the  oils  are  saponified  by  means  of 
caustic  soda  or  caustic  potash. 

Soluble  compounds  are  made  on  lines  similar  to  soluble  oils 
except  that  they  contain  10  per  cent,  to  70  per  cent,  of  water  and 
are  in  a  semi-solid  and  semi-emulsified  condition. 

Cutting  oils  are  sometimes  used  as  soluble  oils,  for  example, 
Cutting  oil  No.  3  when  it  contains  at  least  5  per  cent,  free  fatty 
acid  will  be  capable  of  forming  an  emulsion  with  water  to  which 
has  been  added  soda  ash  or  borax  in  the  right  proportion.  The 
finished  mixture  must  have  only  a  small  excess  of  alkali,  but  it 
should  be  alkaline  to  prevent  separation  and  formation  of  deposits. 

An  average  mixture  is  as  follows : 

40  gals,  of  water  +1.5  Ibs.  of  soda  ash;  mix  the  oil  with  this 
alkaline  water  to  the  required  strength,  ranging  from  1  gal.  to 
6  gals,  of  cutting  oil. 

It  is  important  that  soluble  oils  or  compounds  be  completely 
and  easily  soluble  in  water,  as  nearly  neutral  as  possible,  do  not 
produce  deposits,  have  rust  preventing  properties  and  possess 
as  much  oiliness  as  possible. 

Solubility. — Soluble  oils  are  easily  dissolved  in  lukewarm  water 
(say  not  below  70°F.  and  preferably  not  above  120°F.)  by  mild 
agitation  and  are  therefore  usually  preferred,  as  soluble  com- 
pounds are  more  or  less  difficult  to  dissolve.  Many  manu- 
facturers incorporate  a  high  percentage  of  water  in  their 
compounds,  as  much  as  50  per  cent,  to  70  per  cent,  which 
makes  it  easier  to  dissolve  them,  but  the  customer  often  pays 
dearly  for  the  water  in  such  diluted  compounds. 

When  emulsions  are  made  from  soluble  compounds  in  small 
quantities,  the  mixing  can  be  done  by  hand  in  an  old  barrel  or 
the  like.  When  large  quantities  are  to  be  made,  good  practice 
is  to  make  a  rich  emulsion,  say  60  per  cent,  of  compound  to 
40  per  cent,  of  water  in  a  smaller  top  tank,  allowing  the  creamy 
emulsion  when  formed  during,  say,  three  days,  to  run  into  a 
large  bottom  tank,  in  which  it  is  diluted  to  the  proper  strength. 
Both  tanks  are  fitted  with  submerged  paddlemixera  with  vertical, 


574  PRACTICE  OF  LUBRICATION 

slowly  revolving  axles.  If  the  paddles  are  not  submerged  or  if 
the  speed  is  too  high,  the  emulsions  become  aerated  and  froth 
vigorously,  whatever  germs  there  may  be  in  the  air  being  thus 
introduced  into  the  emulsion,  which  is  an  excellent  germ  feeder, 
particularly  in  hot  weather.  The  addition  of  a  sterilizing  medium 
like  Lysol  is  very  desirable  under  these  conditions. 

Ammonia  soaps  are  very  easily  emulsified,  so  that  they  are 
frequently  present  in  soluble  oils  or  compounds.  Both  alcohol 
and  ammonia  cause  the  e.mulsion  to  form  readily. 

Occasionally  soluble  oils  after  some  time  in  storage  become 
deficient  in  solubility;  they  may,  for  example,  separate  into 
layers,  or  the  entire  contents  of  the  barrels  may  solidify  into  a 
gelatinous  mass.  This  latter  condition  may  arise  from  an  excess 
of  alkali. 

The  separation  or  decomposition  of  the  oil  is  the  result  of 
defective  preparation.  Evaporation  of  the  alcohol  or  free 
ammonia,  or  decomposition  of  ammonia  soaps  at  ordinary 
temperatures,  or  exposure  to  low  temperatures  may  bring 
about  separation  or  other  changes  in  the  oil,  which  will  affect 
its  solubility. 

When  separation  is  due  to  cold  the  oil  will  in  many  cases  be 
restored  ,to  its  normal  condition  by  warming.  The  soluble  oils 
must  not  contain  too  much  mineral  oil,  preferably  not  more  than 
65  per  cent.,  if  the  emulsions  are  to  remain  stable,  and  it  is 
important  that  the  remainder  of  the  oil  contain  suitable  propor- 
tions of  soap  and  fixed  oils  with  a  resultant  neutral  or  slightly 
alkaline  reaction. 

The  presence  of  rosin  soaps  helps  to  make  the  emulsions  stable, 
possibly  because  of  their  high  specific  gravity.  When  rosin 
soaps  form  part  of  the  soluble  oil,,  the  presence  of  ammonia  soap 
is  desirable,  to  make  the  oil  easily  soluble. 

Acids  and  Alkalies. — Excess  acidity  causes  the  cutting  emul- 
sion to  become  unstable  and  separation  takes  place.  Excess 
alkalinity  tends  to  produce  scum  and  deposits,  and  appears  to 
reduce  the  oiliness  of  the  liquid  and  to  attack  metal  surfaces; 
excessive  wear  of  the  tool  edges  is  often  observed  with  excess 
alkalinity.  The  endeavor  must  therefore  be  to  have  the  emul- 
sions as  near  neutral  as  possible  with  only  a  very  slight  excess  of 
alkali. 

Under  no  consideration  must  the  emulsion  be  acid.  Carbolic 
acid  must  therefore  not  be  used  as  a  disinfectant  as  it  makes  the 
oil  less  soluble;  it  encourages  separation,  and  in  attacking  some 
of  the  alkaline  ingredients  produces  a  troublesome  tenacious 
deposit,  which  is  apt  to  clog  the  pipes.  Lysol  or  similar  disin- 


CUTTING  LUBRICANTS  AND  COOLANTS  575 

fectants  may  be  used  for  sterilizing  emulsions  without  any  ill 
effects. 

Deposits. — The  contents  of  rosin  or  rosin  oil  must  not  exceed 
10  per  cent.,  as  otherwise  the  emulsion  formed  will  be  inclined 
to  throw  down  a  gummy  deposit,  probably  as  a  result  of  air 
oxidation. 

With  cutting  emulsions  made  from  some  grades  of  soluble  oils 
containing  ammonia  the  ammonia  volatilizes  under  severe  con- 
ditions of  service,  and  a  scum  is  produced  on  the  surface  of  the 
emulsion  which  is  objectionable,  as  it  tends  to  clog  the  pipes  in 
the  circulation  system. 

The  fatty  oils  used  must  be  of  good  quality,  as  if  they  are  of  a 
highly  gumming  (drying)  character,  the  emulsions  formed  from 
such  oils  will  oxidize  and  throw  down  deposits. 

Rusting. — The  presence  of  some  rosin  or  rosin  oil  appears  to 
be  desirable  as  it  makes  it  possible  to  use  weak  solutions  on  steel 
parts  without  danger  of  rusting. 

Certain  grades  of  oil  containing  alcohol  have  shown  a  marked 
tendency  to  cause  rusting,  but  it  is  not  certain  whether  the  alco- 
hol was  the  direct  cause,  or  the  unusually  large  percentage  of 
mineral  oil  (70  per  cent,  and  more)  present  in  thtfse  particular 
oils.  Free  alcohol  is  easily  oxidized  exposed  to  heat;  it  may 
eventually  be  transformed  into  acetic  acid,  which  would  im- 
mediately cause  rusting. 

The  use  of  a  stronger  emulsion  will  nearly  always  be  a  cure  for 
rusting,  but  there  is  a  great  difference  between  different  oils  in 
this  respect.  Some  soluble  oils  containing  rosin  soaps  can  be 
used  in  emulsions  as  weak  as  40  :1  without  rusting  steel  parts; 
others  cannot  be  used  weaker  than  10  : 1. 

Oiliness. — Oils  possessing  high  lubricating  power,  as  castor, 
rape  and  lard  oil,  are  excellent  ingredients  to  use  in  soluble  oils, 
and  give  the  emulsions  a  comparatively  great  oiliness.  The 
lower  the  percentage  of  mineral  oil,  and  therefore  the  greater 
the  percentage  of  saponifiable  oils,  the  more  oily  will  the  emul- 
sions be. 

To  have  great  oiliness,  cutting  emulsions  must  contain  only  a 
small  percentage  of  mineral  oil,  and  the  emulsions  should  be 
rich,  i.e.  used  in  proportions  of  4:1  to  6:1.  Such  oily  emul- 
sions may  be  used  for  very  severe  conditions  of  high  cutting 
speed  and  heavy  cuts,  where  great  oiliness  and  excellent  cooling 
properties  are  required. 

The  formulae  for  soluble  oils  and  compounds  are  innumerable 
and  mostly  trade  secrets.  If,  however,  the  points  mentioned 
above  are  studied,  some  little  experimenting  and  experience  will 


576  PRACTICE  OF  LUBRICATION 

enable  chemists  to  work  out  their  own  formulae,  making  use  of 
the  raw  materials  available. 

Much  depends  on  the  care  exercised  in  mixing  and  preparing 
the  soluble  oils,  if  they  are  to  remain  stable  without  losing  their 
solubility,  separating  into  two  or  more  layers  or  becoming 
gelatinous. 


CHAPTER  XXXV 

STATIC  ELECTRICAL  TRANSFORMERS  AND  OIL 
FILLED  SWITCHES 

STATIC  ELECTRICAL  TRANSFORMERS 

The  economical  distribution  of  electrical  energy  for  power 
or  lighting  purposes  has  only  been  made  possible  through  the 
development  of  electrical  transformers,  which  are  now  built  in 
sizes  up  to  20,000  k.w.  and  operating  with  voltages  of  150,000 
volts  or  more. 

Transformers  either  transform  electrical  energy  from  high 
voltage  into  low  voltage — "  step-down  "  transformers — or  from 
low  voltage  into  high  voltage — "step-up"  transformers.  The 
latter  are  used  at  large  power  stations  for  producing  high  tension 
current  for  long  distance  distribution  service.  The  step-down 
transformers  are  used  at  sub-stations  and  receiving  centres  for 
local  distribution  of  low  tension  current. 

Fig.  222  shows  diagrammatically  the  design  of  a  transformer 
for  3-phase  alternating  current.  The  thin  high  tension  coils  (1) 
are  wound  around  an  iron  core  (2)  and  the  thick  low  tension 
coils  (3)  are  placed  outside  the  high  tension  coils  with  a  slight 
space  intervening;  there  are  three  sets  of  cores  and  coils,  one 
set  for  each  phase;  the  iron  cores  are  connected  top  and  bottom 
to  form  a  magnetic  circuit. 

In  this  transformation  of  energy  a  certain  percentage  ranging 
from  1  per  cent,  to  2  per  cent,  is  lost  consisting  chiefly  of  magnetic 
losses  .in  the  iron  core  and  copper  losses  in  the  copper  coils.  The 
loss  is  converted  into  heat  which  must  be  carried  away;  otherwise 
the  coils  become  hot  and  the  insulation  breaks  down,  causing  a 
short  circuit. 

Fibrous  insulation  is  almost  universally  employed  and  if  it  is 
not  to  suffer  must  not  be  heated  to  a  temperature  exceeding 
85°C.  to  100°C. 

Air  Cooled  Transformers. — The  cooling  in  transformers 
below  33,000  volts  can  be  done  by  air,  either  by  natural  draught 
with  small  transformers  or  by  an  air  blast  (1.5  oz.  air  pressure) 
of  approximately  150  cu.  ft.  per  minute  per  k.w.  loss.  This 
will  give  a  temperature  rise  of  the  air  entering  and  leaving  of 
about  15°C.  This  method  is  used  for  transformers  up  to  1,000 
37  577 


578 


PRACTICE  OF  LUBRICATION 


k.w.  or  in  even  greater  sizes,  but  such  transformers  are  not  suitable 
for  out-door  work,  as  they  must  be  cased  in,  and  they  are  likely 
to  have  their  insulations  destroyed  by  condensation  or  dust 
from  the  air. 


•— 


3\  \ 

•  A 


d 


i 


FIG.  222. — Transformer. 


Oil  Cooled  Transformers. — Practically  all  transformers  nowa- 
days are  oil  cooled.  The  coils  and  core  are  immersed  in  the  oil, 
which  acts  as  a  heat  conveying  medium  between  the  coils  and 
the  surrounding  transformer  casing.  In  addition  the  oil  has  a 


STATIC  ELECTRICAL  TRANSFORMERS 


579 


dielectric  strength  about  15  times  greater  than  air;  it  therefore 
helps  to  increase  the  breakdown  resistance  of  the  insulation  and 
tends  to  "heal"  it  in  case  of  a  puncture. 

The  use  of  oil  in  a  transformer  as  compared  with  air  results 
in  more  rapid  dissipation  of  heat,  a  lowering  of  the  core  tem- 
perature and  longer  life  of  the  transformer.  The  dissipation  of 
heat  is  increased  by  making  the  transformer  case  with  deep  ver- 
tical corrugations  which  largely  increase  the  radiating  surface. 
The  corrugated  steel  sheets  forming  the  sides  of  the  transformer 


Ill 


UD 


n 


<&• 


(I 


I 


UD 


FIG.  223. — Jacketed  oil  cooled  transformer. 

tank  are  welded  together  and  are  cast  into  the  base  and  the  top 
rim.  Such  self-cooled  transformers  are  limited  to  about  500  k.w. 
capacity  and  in  order  to  increase  the  capacity  it  becomes  neces- 
sary to  increase  the  efficiency  of  the  oil  cooling  arrangements. 

This  may  either  be  done  by  further  increasing  the  radiating  sur- 
face or  by  the  introduction  of  a  cooling  coil  in  the  upper  part  of  the 
transformer  through  which  is  passed  a  slow  stream  of  cold  water. 
Fig.  223  illustrates  a  jacketed  transformer  tank  which  can  be 
employed  up  to  2,000  k.w.  capacity.  The  transformer  tank  proper 
is  surrounded  by  one  or  more  jackets  connected  to  the  main 
tank  at  the  top  and  bottom  by  tubular  openings  through  which 
the  hot  oil  at  the  top  flows  into  the  jackets  and  on  being  cooled 


580 


PRACTICE  OF  LUBRICATION 


sinks  slowly  clown  through  the  jackets,  re-entering  the  trans- 
former tank  through  the  bottom  connections.  There  will  be 
a  rapid  circulation  of  air  up  through  the  space  between  the 
jackets  and  between  the  jackets  and  the  tank,  which  serves  to 
remove  quickly  the  heat  from  the  hot  oil. 

A  further  increase  in  the  radiating  surface  is  obtained  in  the 
construction  illustrated  Fig.  224.  Several  radiators  are  distrib- 
uted in  radial  fashion  around  the  transformer  tank,  being  con- 
nected to  the  latter  by  tubes  top  and  bottom,  through  which  the 


jy 


FIG.  224. — Transformer  with  radiators. 

oiljjenters  the  radiators  at  the  top  and  re-enters  the  tank  at  the 
bottom.  The  radiators  must  be  so  designed  that  there  are  no 
"pockets."  Such  transformers  have  been  constructed  up  to  a 
capacity  of  8,000  k.w. 

Both  in  this  construction  and  the  jacketed  tank  construction 
all  joints  are  thoroughly  welded  to  make  them  absolutely  oil  tight 
and  to  provide  a  strong  mechanical  construction. 

In  very  large  transformers  or  in  transformers  which  are  subject 
to  occasional  heavy  overloads  the  cooling  of  the  oil  by  means  of 
a  water  cooling  coil,  as  illustrated  in  Fig.  225,  has  been  successful 
for  indoor  work  and  also  for  such  outdoor  work  where  the  condi- 


STATIC   KLl'XTIWAL  TRANSFORMERS 


581 


lions  permit  of  cooling  coils  being  employed.  These  cooling  coils 
are  made  of  seamless  copper  tubing  in  order  that,  there  may 
be  no  leakage  of  oil  into  the  transformer. 

The  cooling  coils  must  be  kept  entirely  immersed  in  the  oil,  as 
otherwise  sweating  will  occur  and  the  water  will  contaminate  the 
oil.  The  coils  may  be  so  arranged  that  the  water  can  be  entirely 
drained  off  to  prevent  freezing  when  the  transformer  is  out  of  use 


FIG.  225. — Water  cooled  transformer. 

and  exposed  to  low  temperatures.  When  the  cooling  water  enters 
and  leaves  through  the  cover,  it  is  important  to  wrap  the  short 
pieces  of  cooling  coil  not  immersed  in  the  oil  with  layers  of  tape 
to  prevent  condensation. 

The  cooling  coils  are  usually  from  1  inch  to  2  inches  in  diameter, 
the  length  depending  upon  the  amount  of  heat  to  be  carried 
away  and  the  difference  in  temperature  between  the  oil  and  the 
water.  Current  practice  is  to  have  a  cooling  surface  in  con- 
tact with  the  oil,  ranging  from  500  to  1300  square  inches  per 
k.w.  of  total  transformer  loss. 


582  PRACTICE  OF  LUBRICATION 

The  cooling  coil  is  made  large  enough  to  permit  lifting  the 
transformer  from  its  case  without  disturbing  the  coil  or  its- 
connections. 

The  cooling  coils  must  not  be  used  under  low  or  medium  load, 
as  the  result  may  be  a  lowering  in  temperature  of  the  transformer 
oil  below  that  of  the  surrounding  air,  which  would  cause  the 
transformer  to  sweat.  Some  water  cooled  transformers  are 
provided  with  a  special  thermometer,  so  arranged  that  in  case 
the  .temperature  exceeds  the  permissible  limit  an  electrical  alarm 
is  operated.  It  would  seem  equally  desirable  to  operate  auto- 
matically the  alarm  when  the  temperature  becomes  too  low  (danger 
of  sweating) .  It  might  even  be  advisable  to  put  the  cooling  coils 
out  of  action  automatically  when  the  temperature  becomes  too 
low  and  into  action  when  the  temperature  reaches  a  certain 
point,  leaving  the  alarm  to  come  into  play  when  the  temperature, 
notwithstanding  the  cooling  coils,  reaches  the  danger  limit. 

Water  cooled  transformers  have  been  made  as  big  in  size  as 
40,000  k.w.  capacity.  Adding  a  water  cooling  coil  to  a  trans- 
former designed  as  a  self-cooling  unit  may  enable  the  trans- 
former to  carry  a  50  per  cent,  greater  load. 

Placing  a  self-cooling  transformer  above  an  air  pit  may  enable 
it  to  carry  a  30  per  cent,  bigger  load,  as  the  rapid  currents  of  air  past 
the  casing  appreciably  increase  the  heat  radiation  from  the  tank. 
Transformers  may  also  be  cooled  by  circulating  the  transformer 
oil  through  a  cooler  independent  of  and  separate  from  the  trans- 
former. This  system  is  occasionally  used  in  transformers  above 
1 ,000  k.w.  capacity.  The  heated  oil  is  drawn  from  the  top  of  the 
transformer  and  after  cooling  is  forced  to  enter  the  ducts  in 
the  transformer  windings  and  core  at  the  bottom.  In  order 
to  direct  the  course  of  the  cold  oil,  the  lower  end  of  the  trans- 
former is  enclosed  and  the  only  outlet  for  the  oil  is  upward 
through  the  ducts. 

For  a  10,000  k.w.  unit  there  may  with  this  system  be  a  saving 
in  cost  of  the  complete  transformer  equipment  of  as  much  as 
25  per  cent,  whereas  the  advantages  practically  disappear  for 
units  in  the  neighborhood  of  1,000  k.w. 

An  advantage  with  forced  oil  circulation  is  that  in  case  of  a 
leakage  no  trouble  occurs,  because  the  oil  is  under  pressure,  where- 
as with  a  cooling  coil  immersed  in  the  transformer  tank  itself 
a  leak  will  mean  the  entrance  of  water  into  the  transformer  oil. 

As  exceptional  systems  of  cooling  may  be  mentioned,  that  cooling 
water  has  been  forced  through  the  magnetic  core  or  even  through 
the  low  tension  coils  themselves,  which  have  been  made  in  the 


STATIC  ELECTRICAL  TRANSFORMERS  583 

form  of  heavy  copper  tubes,  the  heat  thus  being  removed  from 
the  very  point  where  it  is  generated. 

Oil  Temperatures. — The  satisfactory  dissipation  of  heat  in. 
an  oil  immersed  transformer  depends  upon  two  factors,  i.  e.,  the 
coil  radiation  and  the  tank  radiation.  The  coils  and  core  must 
have  sufficient  surface  to  give  up  the  heat  to  the  surrounding 
oil  and  to.  the  oil  passing  up  through  the  ducts.  The  transformer 
tank,  radiators  and  cooling  coils,  must  be  capable  of  removing 
or  radiating  this  heat  from  the  hot  oil. 

The  temperature  of  the  oil  is  always  below  the  temperature  of 
the  coils  or  core  and  in  most  transformers  certain  parts  are  in- 
clined to  heat  more  than  others.  These  "  hot  spots  "  are  therefore 
the  weakest  part  of  the  transformer  and  it  is  the  temperature  of 
these  parts  which  should  be  recorded,  by  means  of  a  resistance 
thermometer  rather  than  taking  the  oil  temperature  by  an  ordi- 
nary thermometer. 

Of  course  the  temperature  of  the  oil  taken  a  few  inches  below 
the  level  is  always  of  importance  and  should  be  recorded  in  the 
daily  log,  but  it  would  be  very  advisable  if  transformer  users 
would  insist  upon  knowing  which  are  the  tender  parts  of  their 
transformers,  so  that  they  might  arrange  for  the  temperatures 
of  these  parts  to  be  regularly  recorded. 

As  the  temperature  of  the  insulation  must  not  exceed,  say, 
185°F.,  the  temperature  of  the  oil  must  obviously  be  less  to  give 
the  necessary  margin  of  safety  from  the  point  of  view  of  the 
insulating  material.  Probably  an  oil  temperature  of  170°F. 
should  be  considered  an  absolute  maximum.  Most  transformers 
in  continuous  service  have  oil  temperatures  ranging  from  120°F. 
to  160°F.  and  a  great  many  transformers  operate  with  an  oil 
temperature  of  120°F.  or  less. 

Transformer  Oils. — In  1913  the  Institution  of  Electrical 
Engineers  formed  a  Research  Committee  of  which  the  author 
is  a  member,  with  a  view  to  standardizing  the  tests  on  insulating 
oils.  An  interim  report  was  published  in  the  January,  1915  issue 
of  the  Journal  of  Institution  of  Electrical  Engineers  which  gives 
a  great  deal  of  useful  information. 

In  the  following  chapters  the  author  gives  his  personal  and 
other  views  on  this  subject,  which  may  not  necessarily  be  endorsed 
by  the  above  Committee;  yet  he  has  endeavored  to  present 
the  information  and  ideas  in  such  a  manner  as  he  hopes  will  not 
meet  with  objection  from  any  quarter. 

In  order  to  judge  the  value  of  a  transformer  oil  the  following 
properties  must  be  determined : 


584  PRACTICE  OF  LUBRICATION 

(1)  Insulating  Value. 

(2)  Sludging  Tendency. 

(3)  Thermal  Transference  Value. 

(4)  Flash  Point  and  Loss  by  Evaporation. 

(5)  Cold  test. 

(6)  Free'dom  from  such  acid,  sulphur  or  other  materials 
likely  to  act  detrimentally  on  the  windings  or  the  metals  used  in 
the  construction  of  the  transformer  or  casing. 

1.  Insulating  Value. — When  discussing  insulating  value  of 
oil  there  are  two  terms  which  must  not  be  confused,  viz.  specific 
resistance  and  dielectric  strength. 

Specific  Resistance.  The  specific  resistance  per  cubic  cm.  is 
the  electric  resistance  of  the  oil  as  measured  between  two  metal 
discs  of  known  areas.  It  is  a  simple  test  to  carry  out  and  an 
important  one.  Tests  have  proved  that  the  specific  resistance 
decreases  rapidly  at  high  temperatures  and  becomes  very  low 
for  all  oils  in  the  neighborhood  of  200°F. 

The  specific  resistance  ought  normally  to  be  at  least  5,000,000 
megohm  at  60°F.  and  1,000,000  megohm  at  100°F.  If  the  oil 
contains  small  quantities  of  moisture  or  other  electrically  con- 
ductive impurities,  such  as  metallic  dust,  acid,  alkali  or  salts, 
which  may  be  suspended  or  dissolved  in  the  oil,  the  specific 
resistance  is  much  affected  and  in  this  way  the  presence  of  even 
traces  of  such  impurities  can  be  readily  detected. 

Dielectric  Strength.  The  dielectric  strength  is  the  number  of 
volts  required  to  puncture  a  transformer  oil  between  electrodes 
of  stated  shapes  and  dimensions  immersed  in  the  oil  and  placed 
a  certain  distance  apart,  usually  .15  inch.  There  are  many 
apparatus  designed  for  this  test  and  some  of  the  important  things 
to  keep  in  mind  when  designing  a  suitable  apparatus  are  the 
following  :- 

(1)  The  quantity  of  oil  required  to  make  a  test  should  be  as 
small  as  possible. 

(2)  The  electrodes  should  be  readily  interchangeable  so  that 
various  shapes  (balls,  discs  or  needle  points)  can  be  fitted  as 
desired. 

(3)  The  distance  between  the  electrodes  should  be  capable 
of  easy  and  accurate  adjustment  to  any  desired  distance. 

(4)  It  should  be  easy  to  clean  both  the  vessel  and  the  electrodes 
after  each  set  of  tests,  so  that  there  will  be  no  danger  of  contami- 
nating the  next  oil  to  be  examined. 

The  dielectric  strength  when  tested  between  various  shapes 
of  electrodes  varies  considerably,  and  sufficient  tests  have  not 


STATIC  ELECTRICAL  TRANSFORMERS  585 

been  carried  out  to  give  a  close  specification  at  various  standard 
temperatures  and  between  various  standard  electrodes. 

The  use  of  two  needle  points  is  not  to  be  recommended  because 
of  the  small  volume  of  oil  subject  to  electric  stress.  When  using 
a  needle  point  and  disc  or  two  discs  a  fairly  large  amount  of  oil 
is  subjected  to  electric  stress  and  the  electric  s*park  has  many 
paths  to  choose,  so  that  if  the  oil  contains  dust  or  moisture  or 
salts  in  solution  the  test  will  be  more  searching  than  with  two 
needle  points. 

Spherical  electrodes  are  now  often  used  and  the  actual  size 
does  not  appear  to  be  of  any  particular  importance.  J.  L.  Lang- 
ton  informs  the  author  that  when  carrying  out  tests  at  100°C., 
using  spheres  with  a  gap  of  .15  in.  he  finds  scracely  any  difference 
between  .  393  in.,  .5  in.  and  1  in.  diameter.  He  found  a  difference 
of  only  6  per  cent,  between  1  in.  and  .5  in.  sphere,  the  former 
giving  the  higher  value. 

When  the  oil  is  moist  the  dielectric  strength  will  be  low,  so 
that  when  testing  for  dielectric  strength  it  is  customary  to  heat 
and  dry  the  oil  before  carrying  out  the  test,  unless  the  object 
of  the  test  is  to  detect  the  presence  of  moisture. 

The  dielectric  strength  of  an  oil  increases  with  rise  in  tempera- 
ture, the  increase  found  by  various  investigators  ranging  from 
.1  kilo  volts  to  .3  kilovolts  per  °F.  The  dielectric  strength  is, 
however,  highest  when  the  oil  is  congealed  by  freezing,  probably 
because  small  specks  of  dust  and  moisture  then  are  incapable  of 
moving  into  line,  which  would  facilitate  the  formation  of  a  spark. 

J.  L.  Langton  makes  the  following  remarks,  which  show  the 
effect,  of  the  presence  of  moisture,  all  tests  being  carried  out 
between  spherical  electrodes  and  with  a  gap  of  .15  in.: 

"  Generally  oils  at  a  temperature  of  100°C.  give  a  value  of  60  kilovolts. 
A  falling  off  in  the  break  down  voltage  is  noticed  as  the  oil  cools,  which 
I  think  is  either  due  to  condensation  into  larger  drops  of  tiny  moisture 
or  steam  particles  locked  up  in  the  oil  even  after  heating  at  100°C.  to 
120°C.  or  else  due  to  actual  breathing  action  of  the  oil  absorbing  mois- 
ture from  the  air. 

The  break  down  voltage  at  20°C.  varied  between  20  and  30  kilovolts, 
(say  25  kilovolts)  for  most  of  the  transformer  oils  after  cooling  (i.e.,  and 
therefore  also  after  absorption  or  condensation).  I  think  -one  should  ex- 
pect a  break  down  voltage  of  27  kilovolts  on  a  fairly  dry  oil.  The  ave  age 
on  a  very  dry  good  oil,  when  tested  immediately  after  prolonged  heating 
and  allowed  to  cool  in  an  oven  to  normal  temperature  is  40  kilovolts. 

Actually  on  account  of  moisture  in  most  of  the  oils  received,  I  obtained 
an  average  of  16  kilovolts.7' 

With  transformer  oils  of  good  quality  the  dielectric  strength 


586  PRACTICE  OF  LUBRICATION 

when  tested  after  drying  the  oil  should  be  not  less  than  the  fol- 
lowing values  when  determined  at  100°F. 

Electrodes  placed  .15  in.  apart  Dielectric  strengtn  in  volts 

Two  %-in.  balls.  20,000  volts. 

Needle  point  and  M-in.  disc.  11,000  volts. 

"Some  experiments  were  carried  out  by  Messrs.  T.  Hirobe,  W.  Ogawa 
and  S.  Kubo  of  the  Electric  Technical  Laboratory  of  Department  of 
Communications,  Tokio,  (Report  No.  25  of  the  3rd  Section  of  the 
Laboratory)  as  a  result  of  which  they  suggest  that  the  increase  in  dielec- 
tric strength  usually  observed  when  heating  transformer  oil  may  be  due 
to  the  partial  drying  of  any  fibrous  hygroscopic  substance  present  in  the 
oil.  They  also  consider  that  the  effect  of  moisture  is  slight  as  long  as 
dust  is  absent. 

Oil  dissolves  very  little  water,  only  about  0.01  per  cent.;  with  greater 
amounts  of  water,  oil  forms  emulsions,  the  particles  agglomerating  sooner 
or  later,  and  if  such  water  particles  settle  on  the  insulators,  e.g.,  on  a 
high  tension  coil  immersed  in  oil,  their  effect  may  be  disastrous. 

Dust  particles,  especially  when  fibrous,  absorb  moisture;  such  fibres 
readily  bridged  the  electrode  gap  in  the  dielectric  strength  testing  appa- 
ratus and  caused  breakdown.  Thus  the  breakdown  voltage  of  a  good  oil 
occurred  at  from  90  down  to  60  kv.  (using  /^-in.  ball  electrodes  with  a 
gap  of  .15  in.)  as  the  moisture  increased;  when  the  electrodes  were 
"cleaned  "by  being  rubbed  with  a  dry  cotton  cloth  a  similar  curve  was 
obtained,  but  the  breakdown  occurred  at  from  35  down  to  15  kilovolts. 
In  a  high  tension  transformer  the  dust  is  attracted  towards  the  high  ten- 
sion coil  and  accumulates  on  it.  Fortunately,  filtering  through  a  proper 
filter  press  removes  both  moisture  and  dust,  and  it  is  recommended  to 
keep  the  oil  of  high  tension  transformers  in  constant  circulation." 

Apart  from  the  influence  of  temperature  on  dielectric  strength, 
it  is  quite  certain  that  small  percentages  of  moisture  decrease 
the  dielectric  strength  appreciably.  It  is  very  difficult  to  deter- 
mine small  percentages  of  water  with  any  degree  of  accuracy, 
which  explains  why  the  figures  quoted  by  different  investigators 
differ  considerably;  but  the  following  results  being  the  average 
from  various  sources  will  indicate  the  serious  effect  of  moisture. 

Moisture  in  percentage  Dielectric  strength  in  percentage 

Nil.  100  per  cent. 

.01  per  cent.  65  per  cent. 

'.02  per  cent.  50  per  cent. 

.  10  per  cent.  25  per  cent. 

As  oil  in  time  may  absorb  .01  per  cent,  of  moisture  when  exposed 
to  the  atmosphere,  it  may  be  concluded  that  where  transformer 
casings  are  not  hermetically  sealed  one  cannot  reckon  on  a 
dielectric  strength  of  more  than  half  or  two-thirds  of  the  value 
for  dry  oil. 


STATIC;  ELECTRICAL  TRANSFORMERS  587 

When  the  cooling  coils  inside  the  transformer  have  sweated 
or  when  they  have  cooled  the  oil  below  the  temperature  of  the 
atmosphere,  the  condensation  may  have  further  reduced  the 
dielectric  strength  of  the  oil. 

Dust,  especially  if  metallic,  is  as  effective  as  water  in  reducing 
dielectric  strength.  Dust  will  enter  the  transformer  casing  when 
it  is  not  hermetically  sealed,  and  the  amount  of  dust  will  of 
course  depend  on  the  cleanliness  of  the  air  in  the  transformer 
room.  When  transformers  are  being  stored  out  of  their  tanks, 
great  care  must  be  taken  to  prevent  dust  accumulating  on  the 
windings  and  any  dust  present  must  be  carefully  removed  before 
the  transformer  is  again  put  into  service. 

Dust  may  also  be  introduced  with  the  transformer  oil.  In 
one  case  the  oil  was  found  to  contain  a  very  fine  steel  dust  which 
had  come  from  the  inside  of  the  steel  drums  in  which  the  oil 
was  shipped.  The  dust  was  so  fine  that  it  kept  more  or  less  in 
suspension  in  the  oil  and  had  to  be  removed  by  careful  filtration 
in  a  filter  press  before  the  oil  was  fit  for  service. 

In  view  of  the  above  it  will  be  realized  that  it  is  of  the  greatest 
importance  before  putting  the  transformer  oil  into  use  that  the 
oil  be  carefully  dried  and  filtered. 

The  oil  must  be  tested  for  dielectric  strength  not  only  before 
use  but  also  periodically  during  service.  Oils  which  are  badly 
refined  often  show  low  dielectric  strength.  This  is  due  to  the 
presence  of  alkali  acid  or  salts.  It  is  therefore  important  that 
transformer  oils  be  most  carefully  refined,  so  as  to  remove  as 
nearly  as  possible  all  traces  of  alkali,  acid,  or  salts. 

While  the  presence  of  free  sulphur  is  said  to  have  an  effect  on 
tho  dielectric  strength  of  oil,  the  greater  danger  lies  in  the  fact 
that  even  in  minute  quantities  it  vigorously  attacks  copper.  In 
some  oils  small  amounts  of  sulphur  exist  in  strong  chemical  com- 
bination. Such  sulphur  compounds  have  not  been  proved  to 
be  deleterious,  probably  because  it  is  so  difficult  to  decompose 
them. 

2.  Sludging  Tendency. — -The  question  of  sludging  in  trans- 
former oils  has  during  recent  years  become  very  prominent. 

Transformers  used  to  deal  chiefly  with  electric  lighting  loads 
which  allowed  them  to  have  a  rest  and  cool  down  in  between 
the  peak  loads,  but  transformers  are  now  worked  continuously 
at  high  loads  owing  to  the  large  amount  used  for  power  purposes. 
Increased  competition  creates  a  desire  on  the  part  of  transformer 
makers  to  make  the  transformers  as  small  as  possible,  which  in 
turn  means  higher  oil  temperatures.  High  oil  temperatures 


588  PRACTICE  OF  LUBRICATION 

therefore  now  prevail  and  it  is  the  high  oil  temperatures  which 
through  oxidation  bring  about  the  formation  of  sludge. 

Sludge  usually  contains  a  large  volume  of  oil  and  is  soft  and 
slimy.  Occasionally  it  may  be  of  a  more  solid  nature,  of  dark 
chocolate  color  and  much  resembling  the  deposits  produced  in 
turbine  oil  systems  caused  by  oxidation.  The  sludge  clings  to 
the  sides  and  bottom  of  the  transformer,  and  what  is  more  serious 
it  settles  on  the  windings  and  chokes  the  ventilating  ducts,  thus 
obstructing  the  heat  flow  into  the  oil.  In  water  cooled  trans- 
formers the  water  cooling  coils  seem  to  attract  the  sludge,  which 
in  fact  always  seems  to  settle  out  where  there  is  a  sudden  fall 
in  temperature.  The  formation  of  sludge  is  accompanied  by  an 
increase  in  acidity,  viscosity,  and  specific  gravity,  a  slight  lower- 
ing of  the  flash  point  and  a  considerable  darkening  in  color. 

Sludge  is  always  very  acid,  much  more  so  than  the  transformer 
oil.  The  acids  are  weak  petroleum  acids  which  do  not  appear 
to  affect  the  insulation  or  attack  the  metals  of  which  transformers 
are  usually  made.  Transformer  oil  having  an  acidity  as  high  as 
0.3  per  cent,  in  terms  of  SO3  has  not  shown  any  ill  effects. 

Before  sludge  is  actually  produced  in  a  transformer  the  oil 
darkens  considerably  in  color.  The  darkening  in  color  cannot 
be  used  as  an  accurate  guide  as  to  when  sludging  does  occur, 
but  it  is  distinctly  a  sign  of  warning,  showing  that  the  oil  is 
beginning  to  oxidize  and  break  down. 

The  mere  heating  of  oil  does  not  produce  deposit.  Oils  have 
been  heated  for  long  periods  to  temperatures  approaching  their 
flash  points  and  when  such  heating  has  taken  place  without  the 
access  of  air,  no  deposit  has  formed.  In  the  same  way  heating 
oil  in  the  presence  of  an  inert  gas  like  carbonic  acid  or  nitrogen 
does  not  appear  to  have  any  effect. 

It  has  been  suggested  that  sludging  may  be  caused  by  electro- 
static stress,  the  hydrocarbons  decomposing  as  mentioned  under 
turbine  oils.  A  discharge  of  current  through  the  oil  will  bring 
about  such  decomposition.  It  is  generally  agreed,  however, 
that  this  cause  cannot  be  responsible  for  the  many  frequent 
cases  of  sludging  now  met  with. 

Practically  all  sludge  developed  in  transformers  when  analyzed 
will  be  found  to  contain  a  considerable  percentage  of  oxygen. 
Dr.  A.  C.  Michie  reports  the  following  composition  of  a  typical 
deposit : 

Carbon 74.3  per  cent. 

Hydrogen 6.6  per  cent. 

Oxygen 1 9. 1  per  cent, 


STATIC  ELECTRICAL  TRANSFORMERS  580 

Dr.  Michio  has  shown  that  deposits  of  very  similar  charartoris- 
tics  are  produced  when  transformer  oils  are  oxidized  by  passing 
a  current  of  air,  ozonized  air  or  oxygen,  through  the  oil  heated  to 
a  temperature  ranging  from  100°C.  to  150°C.  The  percentage 
of  sludge  formed  will,  of  course,  depend  on  the  oxidizing  medium 
and  the  temperature.  The  percentage  of  sludge  formed  is 
increased  several,  times  in  the  presence  of  metallic  copper  which 
acts  as  a  catalyst.  Since  Dr.  Michie  in  1913  published  the  results 
of  these  very  important  experiments  his  theory  as  to  the  forma- 
tion of  sludge  in  transformer  oil  has  been  widely  accepted  and 
all  indications  point  to  oxidation  of  the  transformer  oil  as  being 
the  chief  cause  of  sludge  formation. 

When  a  transformer  is  put  under  load  the  temperature  in- 
creases and  the  oil  expands.  Later  on  when  the  load  is  reduced 
the  temperature  decreases  and  the  oil  level  falls.  As  a  result 
of  the  oil  alternately  expanding  and  contracting  " breathing'1 
takes  place,  the  air  being  expelled  from  the  top  of  the  casing  or 
again  drawn  in,  assuming  that  the  casing  is  not  hermetically 
sealed.  Such  breathing  continuously  introduces  new  volumes 
of  air  together  with  dust,  impurities  and  moisture. 

Ozone  may  be  produced  in  the  transformer  and  will  accelerate 
the  oxidizing  effect  of  the  air  on  the  oil.  Most  dust  from  the  air 
is  very  thinly  coated  with  a  layer  of  ozone  which  assists  in  ac- 
celerating oxidation  of  the  oil.  It  would  appear  that  to 
largely  minimize  or  entirely  overcome  the  oxidation  effects,  it 
will  be  necessary  to  prevent  the  air  having  access  to  the  trans- 
former casing  or  one  must  be  content  to  operate  with  lower  oil 
temperatures. 

Some  modern  transformers  are  therefore  now  made  with 
hermetically  sealed  tanks  having  an  expansion  chamber  in  which 
the  oil  can  expand  or  contract,  but  in  which  no  new  air  is  intro- 
duced during  the  normal  operation  of  the  transformer. 

A  combination  relief  and  vacuum  valve  is  fitted  to  prevent 
excess  pressure,  which  would  burst  the  tank,  or  excess  vacuum, 
which  would  cause  the  tank  to  collapse.  The  lids  may  be  made 
very  weak  or  arranged  to  blow  off  quickly  in  case  of  abnormal 
pressure  caused  by  a  short  circuit.  Other  transformers  have 
breathers  attached  to  the  transformer  tanks  which  are  provided 
with  traps  to  extract  the  moisture  from  the  air  which  is  inhaled 
as  the  transformer  cools  and  the  oil  shrinks. 

Sub-way  transformers  which  are  particularly  exposed  to  dust 
and  high  temperatures  are  practically  always  made  with  air- 
tight covers  ,and  rather  large  air  spaces  above  the  oil  level  to 
take  care  of  the  expansion  of  the  oil  under  heat  without  creating 


590  PRACTICE  OF  LUBRICATION 

undue  pressure.  Provision  should  be  made  to  prevent  excess 
pressure  (caused  by  heavy  overloads)  by  fitting  a  pressure  relief 
valve  or  other  safety  device.  A  simple  device,  apart  from  those 
mentioned,  is  to  put  a  float  on  top  of  the  oil.  The  oil  at  the 
bottom  and  sides  is  already  out  of  contact  with  the  atmosphere, 
and  with  a  properly  fitted  float  which  will  rise  and  fall  with  the 
oil  very  little  air  can  get  to  it. 

It  is  difficult  to  say  .at  what  temperatures  sludging  can  be 
absolutely  prevented.  The  temperature  at  which  sludging  takes 
place  depends  largely  on  the  condition  of  the  transformer,  i.e. 
whether  the  air  has  free  access  to  the  tank  or  whether  it  is  more 
or  less  sealed;  and  it  also  depends  very  largely  on  the  quality  of 
the  transformer  oil.  Non-sludging  transformer  oils  have  been 
produced  during  recent  years  which  have  only  a  very  small  tend- 
ency to  oxidize  as  shown  when  subjected  to  the  following  oxida- 
tion test,  which  is  the  original  test  proposed  by  Dr.  Michie. 

"One  hundred  c.c.  of  the  oil  is  placed  in  a  200  c.c.  flask  and  main- 
tained at  150°C.  for  45  hours,  during  which  period  dry  air  is  passed 
slowly  through  the  oil  at  the  rate  of  0.066  cu.  ft.  per  hour,  a  piece  of 
copper  with  a  total  surface  area  4^  sq.  in.  being  placed  in  the  oil." 

Mos*  transformer  oils,  when  not  particularly  well  refined,  will 
produce  1  per  cent,  of  deposit  or  more  when  subjected  to  his  test. 
So-called  " non-sludging"  oils,  whether  of  American  or  Russian 
make,  do  not  produce  any  deposit  by  this  test  when  the  tempera- 
ture is  maintained  at  120°C.  but  at  150°C.  most  oils,  even  the  best, 
produce  some  deposit,  say  0.05  per  cent,  or  less.  Pale  oils  generally 
produce  less  deposit  than  dark  colored  oils.  " Non-sludging ". 
oils  are  water  white  or  almost  water  white  in  color,  particularly 
the  Russian  oils.  It  is  difficult  to  remove  the  last  trace  of  color 
from  American  oils. 

Obviously,  when  .transformers  are  hermetically  sealed  and 
using  " non-sludging"  transformer  oil  a  very  much  higher  operat- 
ing temperature  can  be  permitted  with  safety,  say  160°F.,  than 
when  transformers  are  not  hermetically  sealed  and  placed  in 
dirty  surroundings,  in  which  case  the  temperatures  ought  never 
to  exceed,  say,  120°F. 

Deposits  have  also  been  due  to  the  oil  attacking  the  insulating 
compounds,  as  a  fair  number  of  deposits  have  been  found  to 
contain  lead  and  manganese. 

3.  Thermal  Transference. — The  transference  of  heat  through 
the  oil  usually  takes  place  by  convection  circulation  of  the  oil. 
The  oil  in  contact  with  the  transformer  windings  absorbs  heat  and 
rises  to  the  surface,  while  the  oil  near  the  inside  of  the  transformer 
casing  cools  and  sinks  to  the  bottom.  The  circulaton  of  the 


STATIC  ELECTRICAL  TRANSFORMERS 


591 


oil  is  duo  to  tho  change  in  specific  gravity  caused  by  the  differ- 
ence in  temperature  between  the  oil  in  the  centre  and  the  oil  at 
the  outside. 

Fig.  226  illustrates  diagrammatically  an  apparatus  suggested 
by  the  author  for  testing  the  thermal  transference  of  transformer 
oils.  The  oil  is  heated  in  the  thin  tube  (1)  and  cooled  in  the  wide 
tube  (2)  the  idea  being  that  the  thin  tube  will  correspond  to  the 
vertical  ducts  in  the  centre  of  the  transformer  and  the  wide  tube 
to  the  descending  columns  of  oil  near  the  inside  of  the  casing. 
The  National  Physical  Laboratory  made  some  theoretical  calcu- 
lations based  on  this  apparatus  and  arrived  at  the  following 
formula  for  the  thermal  transference: 


FIG.   226. — Thermal  transference. 

Thermal  Transference  =  -S  X  D  X  E/V. 

8  =  The  specific  heat  of  the  oil  at  the  mean  working 
temperature. 

D  =  The  density  of  the  oil  at  the  bottom  of  the  trans- 
former. 

E  =  The  coefficient  of  expansion. 

V  —  The  viscosity  of  the  oil  at  the  mean  working  tem- 
perature. 

In  comparing  transformer  oils  made  from  paraffin  base  crudes 
and  transformer  oils  made  from  Russian  crudes,  it  is  found  that 
paraffin  base  oils  have  approximately  10  per  cent,  higher  specific 
heat  and  10  per  cent,  lower  specific  gravities  than  Russian  oils. 
The  coefficient  of  expansion  is  approximately  the  same,  so  that 
if  the  above  formula  gives  a  correct  indication,  it  would  appear 
that  the  thermal  transference  of  different  transformer  oils  is 
inversely  related  to  their  viscosity. 

Russian  transformer  oils  are  higher  in  viscosity  than  paraffin 
base  transformer  oils,  but  the  difference  is  not  so  marked  at  the 


592  PRACTICE  OF  LUBRICATION 

working  temperature  of  the  transformers  us  will  In*  scon  from  tho 
following  table: 

Saybolt  Viscosity 


@120°F., 


@170°F 
in. 


Typical  Russian  White  Transformer  Oil 100  52 

Typical  American  Pale  Transformer  Oil 56  41 


The  thermal  transference  value  of  American  transformer  oils 
might  therefore  be  expected,  speaking  generally,  to  be  higher 
than  the  thermal  transference  value  of  Russian  oils,  but  it  must 
not  be  overlooked  that  it  is  extremely  difficult  to  produce  non- 
sludging  transformer  oils  from  paraffin  base  crudes  and  that  the 
sludging  tendency  is  a  very  important  factor  in  comparing  the 
value  of  two  oils.  If  one  oil  produces  even  a  small  amount  of 
sludge  compared  with  another  oil  which  is  non-sludging,  preference 
should  be  given  to  the  latter,  notwithstanding  its  higher  viscos- 
ity. Sludge  is  &  bad  conductor  of  heat  and  will  easily  cause 
the  temperature  of  the  coils  to  increase  appreciably,  which  in 
turn  means  increased  electrical  loss,  as  the  electric  resistance 
of  metals  increases  with  rise  in  temperature. 

If  the  sludging  tendency  of  the  two  oils  is  the  same,  the  one 
having  the  lower  viscosity  should  be  preferred,  as  it  will  produce 
quicker  circulation  of  the  oil  and  a  more  rapid  transfer  of  heat  to 
the  casing.  As  the  heat  eventually  radiated  from  the  casing 
will  be  approximately  the  same  with  the  two  oils,  it  necessarily 
follows  that  the  temperature  of  the  casing  itself  will  not  be  very 
different,  but  the  more  viscous  of  the  oils  will  be  somewhat  higher 
in  temperature  than  the  lower  viscosity  oil,  so  that  the  maximum 
temperature  of  the  windings  and  core  will  also  be  higher. 

A  low  viscosity  oil  has  the  further  advantage  over  a  viscous 
oil  of  separating  more  easily  from  impurities,  such  as  dust  and 
water. 

4.  Flash  Point  and  Loss  by  Evaporation. — Transformer  oils 
must  be  of  low  viscosity  and  therefore  have  low  flash  points, 
but  the  flash  points  must  not  be  too  low,  as  if  the  oils  are 
very  volatile,  they  will  lose  a  great  deal  by  evaporation  during 
service. 

The  lowest  flash  point  oils  used  for  transformer  service  are 
mineral  seal  transformer  oils  which  are  really  high  flash  point 
burning  oils  having  a  closed  flash  point  of  about  265°F.  These 
oils  are  used  only  for  water  cooled  transformers  where  the  tern- 


STATIC  ELECTRICAL  TRANSFORMERS  "  593 

perature  is  under  absolute  control  and  kept  low,  say  not  exceed- 
ing 120°  F.-130°F. 

Transformer  oils  usually  have  closed  flash  points  somewhat 
above  300°F.  (320°F  to  350°F.)  and  with  such  flash  points 
the  loss  by  evaporation  will  be  found  to  be  reasonably  small  at 
normal  transformer  temperatures,  say,  less  than  0.25  per  cent, 
when  heating  70  grammes  of  oil  for  6  hours  at  100°C.  in  a 
beaker  4  in.  high,  2J£  in.  in  diameter  in  a  hot  oven. 

5.  Cold  Test. — Where  transformers  are  used  in  cold  countries, 
transformer  oil  should  preferably  have  a  good  cold  test.  This 
point  is,  however,  not  of  supreme  importance,  except  with  very 
low  temperatures,  as  during  the  working  of  the  transformer  the 
oil  soon  becomes  warm  and  fluid.  It  is  customary  to  use  oils 
having  a  cold  test  of  about  15°F. 

Treating  Transformer  Oils. — Various  means  are  employed 
for  dehydrating  and  cleaning  transformer  oils.  Oil  will  dissolve 
about  .01  per  cent,  of  moisture,  but  it  may  contain  as  much 
as  .75  per  cent,  in  emulsion  or  in  suspension,  which  will  sepa- 
rate out  only  with  difficulty.  Any  water  in  excess  of  .75  per 
cent,  will  separate  out  when  the  oil  is  heated  to  a  temperature 
of  80°C.  and  can  be  drained  away. 

Some  makers  have  made  use  of  chemicals  such  as  calcium  chlo- 
ride or  calcium  oxide  (unslaked  lime).  The  oil  is  forced  through 
a  receptacle  containing  these  chemicals  and  afterwards  forced 
through  dry  sand.  These  methods  are  antiquated  and  not  to 
be  recommended  if  used  alone.  Other  makers  remove  moisture 
from  the  oil  by  heating  it  to  a  temperature  preferably  not  exceed- 
ing 80°C.  and  either  under  atmospheric  pressure  or  assisted  by 
a  partial  vacuum. 

The  dehydration  will  be  much  accelerated  by  allowing  dry 
air  to  bubble  slowly  through  the  oil.  The  air  should  be  freed 
from  moisture  by  first  passing  through  calcium  chloride  or  un- 
slaked lime. 

Samples  of  oil  should  be  removed  from  time  to  time  and  tested 
electrically  or  by  immersing  into  the  oil  a  M~m-  ir°n  r°d  heated 
to  a  dull  red  heat.  If  any  water  is  present  there  will  be  a  crack- 
ling noise,  whereas  if  the  oil  is  dry,  it  merely  fumes  without  noise; 
.01  per  cent,  of  water  will  be  readily  detected  in  this  manner. 

Transformer  oils  should  preferably  be  shipped  in  steel  drums, 
as  they  are  then  better  protected  from  moisture  than  when 
shipped  in  wooden  barrels.  The  wooden  barrels  have  the  further 
disadvantage  that  glue  from  the  inside  of  the  barrels  may  be 
dissolved  in  tho  oil  and  thus  destroy  its  viiluc  for  transformer 
purposes. 

38 


594  PRACTICE  OF  LUBRICATION 

Steel  drums  or  barrels  used  for  transformer  oils  should  be 
washed  with  naphtha*  to  remove  oil  and  drained,  then  washed 
again  with  clean  naphtha  under  strong  agitation.  The  drums 
should  then  be  placed  in  a  hot  room,  say,  heated  to  200°F.,  and 
kept  in  this  room  with  the  bung  holes  down  for  24  hours.  They 
may  then  be  blown  by  hot  air  to  remove  any  trace  of  vapor, 
after  which  dust  and  loose  sediment  should  be  removed  by  a 
vacuum  pump.  The  drums  should  then  be  bunged  and  trans- 
ferred to  the  filling  room. 

The  transformer  oil  before  being  filled  into  the  drums  should 
be  heated  to  80°C.  and  forced  through  a  filter  press  before  it  is 
delivered  to  the  steel  drums.  The  steel  drums  must  be  kept 
warm  before  filling  to  prevent  condensation  and  must  be  lead 
sealed  directly  after  filling.  The  oil  barrelled  in  this  manner 
will  be  free  from  moisture  and  dust.  If  the  drums  are  not 
effectively  sealed  air  will  be  sucked  into  the  drum,  owing  to 
expansion  and  contraction  of  the  oil  following  upon  temperature 
changes,  and  the  air  introduces  moisture. 

Filter  Presses. — A  typical  filter  press  is  made  up  of  a  number  of 
grids  and  chambers.  Five  sheets  of  dried  and  oiled  filter  paper 
are  placed  between  each  filter  plate  and  the  adjacent  frame,  and 
the  whole  compressed  tightly  together.  The  filter  paper  should 
be  dry,  soft,  white  blotting  paper,  made  principally  from  wood 
pulp  and  free  from  coloring  matter,  chemicals  and  other  foreign 
substances. 

The  oil  is  pumped  by  means  of  a  rotary  multi-stage  centrifugal 
pump  under  a  pressure  of  25"  to  100  Ibs.  per  square  inch  through 
the  blotting  paper  and  discharged  into  the  receiving  tank.  The 
blotting  paper  allows  the  oil  to  pass,  but  retains  all  moisture 
and  impurities.  The  water  will  be  retained  in  the  paper  because 
of  its  greater  capillary  attraction.  This  fact  may  be  illustrated 
by  making  the  following  experiment : 

Take  2  beakers,  one  filled  with  water  and  the  other  filled  with 
oil,  place  a  strip  of  dry  blotting  paper  in  each,  interchange  the 
slips  when  saturated.  In  about  three  minutes  the  oiled  strip 
will  be  thoroughly  saturated  with  water  and  the  oil  driven  out. 
The  strip  which  was  soaked  in  water  will,  however,  not  be  affected 
in  any  way  by  being  immersed  in  the  oil. 

Most  of  the  solid  impurities  in  the  transformer  oil  will  be 
caught  by  the  first  filter  paper,  and  when  the  first  paper  is  satu- 
rated with  water  the  water  will  collect  in  the  second  layer  of 
filter  paper  and  so  on,  until  finally  the  pressure  required  to  force 
the  oil  through  the  press  rises  considerably,  indicating  that  the 
filter  papers  must  be  changed.  After  one  filtration  the  oil  will 


STATIC  ELECTRICAL  TRANSFORMERS 


595 


be  practically  free  from  water,  but  fine  sediment  and  slime  may 
need  more  than  one  filtration  to  be  entirely  removed. 

The  dielectric  strength  of  the  oil  should  be  taken  at  frequent 
intervals  to  determine  when  the  filter  papers  should  be  removed. 
Such  filter  presses  are  made  complete  with  electric  motor,  pump, 
reservoirs,  etc.,  in  portable  form,  so  that  they  can  be  connected 
to  any  transformer  or  transformer  oil  storage  tank.  They  can 
be  applied  to  transformers  during  service.  In  that  case  the  oil 
is  taken  from  the  bottom  of  the  transformer  (Fig.  227),  passed 
through  the  filter  press  and  returned  to  the  top  of  the  transformer 


FIG.  227. — Purifying  transformer  oil. 

tank,  being  kept  in  circulation  until  completely  purified  and 
until  tests  have  shown  that  the  dielectric  strength  or  specific 
resistance  is  satisfactory.  The  first  sheet  of  papers  should  be 
renewed  once  every  half -hour  when  the  oil  is  wet  and  dirty,  while 
for  fairly  dry  and  clean  oil,  once  an  hour  is  sufficient.  The  oil 
is  circulated  at  the  rate  of  from  6  to  20  gallons  per  minute,  accord- 
ing to  the  size  of  the  outfit." 

Where  transformers  are  not  sealed  the  oil  will  in  time  become 
charged  with  hygroscopic  moisture  and  more  or  less  dust,  and  a 
certain  amount  of  sludging  may  occur  due  to  oxidation  of  the 
oil  or  to  action  of  the  oil  on  the  insulating  material. 

For  these  reasons  it  is  good  practice  to  empty  the  transformer 
at  least  once  every  twelve  months,  to  clean  it  thoroughly  from 


596  PRACTICE  OF  LUBRICATION 

sludge  or  deposit  and  carefully  dry  and  filter  the  oil,  preferably 
by  means  of  a  filter  press. 

Starting  a  Transformer. — Before  a  transformer  is  put  into 
its  case  it  is  important  that  the  windings  or  insulating  material 
shall  not  contain  any  moisture  or  air.  A  satisfactory  method 
of  attaining  this  end  is  to  place  the  transformer  inside  a  cylindrical 
shell  which  can  be  hermetically  sealed.  The  temperature  of 
the  interior  of  the  shell  is  raised  by  steam  heating  coils  to  about 
250°F.  so  as  to  evaporate  any  moisture  which  may  be  in  the 
windings.  At  the  same  time  a  vacuum  is  produced  which  will 
cause  any  air  bubbles  or  pockets  in  the  insulation  to  swell  and 
expand,  the  air  being  finally  removed  by  the  vacuum  pump. 

After  sufficient  time  has  passed  to  ensure  the  removal  of  all 
moisture  and  air,  the  tank  is  allowed  to  fill  completely  with  the 
insulating  compound  under  pressure.  When  all  parts  of  the 
insulation  are  thoroughly  impregnated,  the  insulating  compound 
is  drained  out  and  the  windings  dried. 

Coming  back  to  the  erection  of  the  transformer,  the  first  thing 
to  do  when  the  transformer  is  placed  inside  its  case  is  to  have  it 
dried  out  properly  at  a  temperature  of  80°C.  to  90°C.  by  heating 
the  transformer  case,  in  order  that  every  trace  of  absorbed  mois-. 
ture  may  be  removed. 

When  recording  the  temperatures  during  the  drying  out  proc- 
ess, care  should  be  taken  not  to  break  the  thermometers,  as 
drops  of  mercury  might  remain  between  the  windings  and  cause 
a  short  circuit. 

The  transformer  oil  should  be  poured  in  through  four  or  five 
thicknesses  of  cheese  cloth  (or  through  layers  of  unsized  cambric) . 
In  this  way  any  coarse  scale  that  may  have  been  loosened  from  the 
steel  barrels  in  which  the  oil  has  been  shipped  will  be  kept  back. 

Transformer  Explosions. — Explosions  of  transformers  are 
fortunately  very  rare,  but  care  should  always  be  taken  when 
examining  the  transformer  and  removing  the  cover  not  to  have 
naked  lights, .  as  if  the  transformer  has  been  overheated  the  oil 
may  have  given  off  vapors  forming  an  explosive  mixture  with 
the  air  above  the  oil.  Cases  have  been  known  where  violent 
explosions  of  such  vapors  have  occurred,  ignited  by  a  naked 
light. 

Fires  in  transformers  may  result  from  a  short  circuit  or  from 
lightning  or  extreme  overloading,  causing  parts  of  the  windings 
to  overheat,  charring  the  insulation,  and  vaporizing  the  oil.  A 
spark  will  be  produced  by  contact  between  the  windings,  and 
the  oil  is  ignited.  A  short  circuit  in  a  transformer  will  not  set 
fire  to  the  oil  unless  the  arc  is  near  the  surface  of  the  oil,  so  that 


STATIC  ELECTRICAL  TRANSFORMERS  597 

the  surface  may  be  broken  and  the  mixture  of  vaporized  oil  and 
air  ignited. 

In  case  of  fire  the  transformer  itself  may  be  destroyed  or,  if 
the  burning  oil  escapes  from  the  tank,  even  more  serious  damage 
may  occur.  Fire  extinguishers  should  therefore  always  be 
provided. 

Fires  have  been  caused  by  leakage  of  oil  from  the  transformer 
casing  until  parts  of  the  coils  were  above  the  oil  level  and  therefore 
overheated.  It  is  in  order  to  guard  against  such  leakage  that 
all  joints  in  a  transformer  tank  are  usually  welded,  but  leakage 
has  also  been  known  to  occur  by  syphoning,  the  oil  rising  by 
means  of  capillary  attraction  between  the  strands  of  the  cable. 
The  presence  of  oil  on  the  cable  outside  the  transformer  tank  can 
nearly  always  be  detected  by  stickiness  or  the  presence  of  oily 
dust  and  dirt  on  the  floor. 

As  oil  has  a  destructive  effect  upon  the  rubber  insulation, 
destroying  its  mechanical  as  well  as  its  dielectric  strength,  syphon- 
ing of  the  oil  must  be  avoided.  One  method  is  to  solder  the 
strands  of  the  cables  together  for  J^  in.  or  more  above  the  oil 
level,  leaving  a  smooth  surface. 

OIL  SWITCHES 

Oil  filled  switches  have  come  much  into  prominence  during 
recent  years,  one  reason  being  that  the  contacts  if  cleaned  before 
the  oil  is  poured  in  will  keep  clean  and  in  a  condition  of  maximum 
efficiency.  The  main  feature  from  the  oil  point  of  view  in  all 
switches  is  that  every  time  the  contacts  are  broken  an  electric 
spark  is  produced  which  pierces  the  oil,  burns  it  and  produces  a 
certain  amount  of  oil  carbon  and  gas.  The  gas  contains  a  large 
portion  of  hydrogen  and  is  highly  explosive  when  mixed  with 
air,  so  that  the  accumulation  of  gas  is  a  point  which  must  be 
kept  in  mind  when  designing  oil  switches,  particularly  for  use  in 
coal  mines. 

The  majority  of  oil  switches  are  employed  for  A.C.  current, 
but  they  are  not  infrequently  used  for  D.C.  current,  although  in 
such  switches  a  great  deal  more  carbon  is  formed  than  in  A.C. 
switches. 

Some  interesting  experiments  were  carried  out  by  Messrs.  W. 
Pollard  Digby  and  D.  B.  Mellis,  and  recorded  in  a  paper  given 
by  them  before  the  Manchester  Section  of  the  Institution  of 
Electrical  Engineers,  March  22nd,  1910.  They  showed  that  in 
low  viscosity  transformer  oils  the  carbon  particles  quickly 
agglomerated  and  settled  to  the  bottom,  whereas  with  viscous 
oils,  the  carbon  kept  floating  in  the  oil. 


598  PRACTICE  OF  LUBRICATION 

It  is  therefore  important  that  a  switch  oil  should  have  a  low 
viscosity,  so  that  the  carbon  may  separate  out  quickly.  Also  the 
more  fluid  the  oil  the  quicker  will  the  arc  be  quenched  and  the 
less  carbon  will  be  formed.  Switch  oils  should  be  as  free  from 
sulphur  and  sulphur  compounds  as  possible,  as  sulphur  will 
attack  the  copper  contacts. 

The  oil  level  should  be  kept  high  in  the  switch  case  covering 
the  contact  points  to  a  sufficient  depth,  so  that  when  breaking 
even  the  strongest  current,  there  is  no  chance  of  the  spark  break- 
ing through  the  surface  and  igniting  the  gases  that  are  usually 
present  above  the  oil. 

In  order  to  minimize  the  danger  of  an  accumulation  of  gas, 
there  are  two  ways  open,  either  to  ventilate  the  switch  case 
effectively,  so  as  to  give  the  gas  a  chance  to  become  diluted  and 
get  away  from  the  switch  case,  or  to  enclose  the  switch  case 
entirely  and  allow  the  gas  to  create  a  pressure  within  the  switch 
case,  which  is  prevented  from  becoming  excessive  by  means  of 
a  pressure  relief  valve. 

If  the  space  above  the  oil  is  filled  with  the  gas  undiluted  by  air, 
the  gas  cannot  possibly  explode.  The  switch  case,  however, 
must  be  of  sufficient  strength  to  withstand  the  pressure.  When 
switch  cases  are  enclosed  in  this  manner  the  entrance  of  dust 
and  water  is  prevented,  which  is  very  desirable.  The  presence 
of  moisture  in  particular  may  give  rise  to  violent  arcing  and 
extremely  heavy  carbonization.  In  one  case  a  violent  explosion 
in  a  10,000  volt  switch  case  took  place  in  consequence  of  the 
Attendant  throwing  in  the  switch  unphased,  a  powerful  arch 
thus  being  immediately  formed.  The  flames  leapt  8  ft.  high 
and  the  switch  casing  was  twisted  all  out  of  shape.  The  oil 
was  thrown  violently  about  and  was  found  running  all  over  the 
iron  girders  in  the  neighborhood  of  the  switch  casing  and  burn- 
ing. The  oil  on  examination  was  found  to  contain  an  appre- 
ciable percentage  of  moisture.  The  water  during  the  period  of 
arcing  would  immediately  turn  into  steam  and  atomize  the  oil, 
so  that  a  considerable  amount  of  oil  spray  or  oil  fog  would  be 
formed,  thus  accelerating  the  violence  of  the  explosion. 

SPECIFICATIONS  FOR  TRANSFORMER  AND  SWITCH  OILS 

In  formulating  specifications  for  transformer  and  switch  oils 
the  following  schedule  embodies  the  principal  points,  given  in 
their  order  of  importance : 

(1)  The  oil  must  be  a  Highly  refined,  pure  mineral  oil  containing  no  free 
sulphur,  no  resinous,  animal  or  vegetable  matter,  and  no  unstable  sulphurous 
compounds. 


STATIC  ELECTRICAL  TRANSFORMERS  599 

(2)  It  must  contain  only  the  merest  trace  of  acid,  alkali  or  salts. 

(3)  It  must  be  dry  and  well  filtered,  containing  no  dust  or  other  solid  impuri- 
ties. 

(4)  The  dielectric  strength  must  not  be  less  than        kilovolts  when  tested 
between       electrodes  at      °F. 

(5)  The  specific  resistance  must  be  not  less  than          million  megohms  at 
°F.  and  not  less  than         million  megohms  at        °F. 

(6)  The  percentage  of  sludge  must  not  exceed         per  cent,  when  the  oil  is 
subjected  to  (here  follows  description  of  the  oxidation  test). 

(7)  The  viscosity  as  measured  by  the         instrument  must  not  exceed        " 
at        °F. 

(8)  The  closed  flashpoint  must  not  be  less  than        °F. 

(9)  The  loss  by  evaporation  must  not  exceed         per  cent,  when  heating 
grammes  of  oil  for        hours  at        °C.  in  a  beaker        "  high  and        "  in 
diameter  in  (here  follows  description  of  heating  apparatus). 

(10)  The  cold  test  must  not  be  higher  than         °F.  when  tested  by  (here 
follows  description  of  apparatus). 

The  following  test  applies  only  to  switch  oils : 

(11)  When  exposed  to  heavy  sparking  in   (here  follows  description  of 
apparatus)         c.c.  of  oil  must  not  deposit  more  than         grammes  of  carbon 
at        °C.  and  the  carbon  should  quickly  agglomerate  and  separate  from  the  oil. 

(12)  The  sulphur  contents  must  be  as  low  as  possible  and  must  not  exceed 
per  cent. 

The  information  given  in  the  preceding  chapters  will  give  an 
indication  of  the  approximate  figures  which  may  be  specified 
under  the  different  headings,  but  in  view  of  the  fact  that  the 
Insulating  Oil  Committee  of  the  Institution  of  Electrical  Engi- 
neers, when  it  has  completed  its  various  researches  will  for- 
mulate specifications  for  transformer  and  switch  oils,  the  author 
refrains  from  making  his  recommendations  more  definite. 

A  good  qualitjf  transformer  oil  will  always  prove  to  be  a  good 
switch  oil,  although  there  is  no  apparent  reason  why  this  should 
be  the  case.  The  most  important  points  in  the  specification 
as  far  as  switch  oils  are  concerned  appear  to  be: 

Freedom  from  moisture  (3) ; 
High  insulating  value  (4  and  5) ; 

Low  carbon  formation  (11),  which  appears  to  be  more  or  less  related  to 
sludging  tendency  (6); 

Low  viscosity,  to  quickly  quench  the  arc  (7) ; 
Reasonably  high  flash  point  (8). 


APPENDIX 

SKIN  DISEASES  PRODUCED  BY  LUBRICANTS 
(By  Dr.  J.  C.  Bridge) 

1.  Oil  rashes  are,  generally  speaking,  of  two  kinds — the  first 
is  due  to  plugging  of  the  small  glands  at  the  root  of  the  hairs  on 
the  arms  and  legs  of  workers,  the  second  to  mechanical  injury  to 
the  skin  produced  by  metallic  particles  suspended  in  the  cutting 
lubricant. 

(a)  Plugging  of  the  Glands  of  the  Hair  Follicles.  Primarily  this 
is  purely  mechanical;  a  mixture  of  oil  and  dirt  blocks  the  minute 
openings  of  these  glands  and  sets  up  inflammation  round  the 
hair  (f olliculitis) .  The  inflammation  commenced  in  this  way 
may  lead  on  to  suppuration  or  abscess  formation  (a  boil).  If 
many  hairs  are  affected  the  arm  presents  an  appearance  of  a 
crop  of  raised  red  spots  (papules)  with  a  black  spot  as  a  centre, 
or,  if  the  inflammation  has  gone  as  far  as  suppuration  (abscess 
formation),  a  yellow  head. 

(6)  Mechanical  Injury  to  the  Skin  by  Metallic  Particles.  Mi- 
nute metallic  particles  suspended  in  the  cutting  lubricant  may 
produce  injury  to  the  skin.  This  occurs  chiefly  on  the  hands, 
where  two  surfaces  are  rubbed  together,  e.g.  the  skin  between  the 
fingers.  Injury  to  the  skin  may  also  be  produced  on  any  part 
of  the  hands  and  arms  by  wiping  with  a  cloth  or  rag  while  the 
hands  or  arms  are  coated  with  a  film  of  fluid  in  which  metallic 
particles  are  suspended.  Injury  to  the  skin  allows  germs  to 
enter  and  causes  septic  infection.1 

2.  Prevention. — (a)  Cleanliness  of  the  Worker. — Washing  ac- 
commoo!ation  for  workers  in  contact  with  oil  must  be  on  a  liberal 
scale.     Hot  water,  soap  and  scrubbing  brushes  are  essential. 
Workers  should  be  instructed  not  to  wipe  their  hands  on  rags, 
etc.,  before  washing  and  to  avoid  washing  their  hands   in  the 
cutting  compounds. 

1  Author's  Note.  Blood  poisoning  has  also  been  caused  by  bacterio- 
logical infection  of  gluey  moisture  present  in  the  cutting  oil. 

Barrels  after  exposure  have  got  soaked  with  moisture  which  spread  the 
infected  glue  throughout  the  oil  (objectionable  odor)  so  that  wherever  this 
oil  afterwards  came  in  contact  with  the  workers  (hands,  arms,  thighs),  even 
including  the  storesman,  blood  poisoning  set  in. 

600 


APPENDIX  601 

Ether  soap,  which  dissolves  oil,  has  been  found  useful  in  pre- 
venting inflammation  of  the  hair  follicles.  Dusting  the  arms 
with  a  powder  containing  equal  parts  of  starch  and  zinc  oxide 
before  commencing  work  prevents  the  action  of  the  oil  on  the 
skin.  k 

(6)  Cleanness  of  the  Lubricant.  Care  must  be  taken  in  the 
handling  of  the  constituents  before  blending  that  they  have  not 
undergone  changes  (e.g.,  formation  of  free  fatty  acid). 

Constant  removal  of  metal  particles  is  necessary  to  avoid  in- 
jury to  the  skin.  Filtration,  such  as  is  provided  on  the  machines, 
and  centrifugal  action,  are  insufficient  to  remove  the  minute  metal 
particles  which  may  injure  the  skin.  Where  cutting  oils  (straight 
oils)  are  used,  their  viscosity  can  be  diminished  by  heat  suffi- 
ciently to  allow  the  particles  to  sink  without  affecting  their  value 
as  lubricants.  This  operation  completely  removes  all  metal  par- 
ticles. In  other  lubricants  where  such  a  procedure  is  impossible 
it  is  necessary  constantly  to  change  and  renew  the  cutting 
lubricants. 

(c)  Cleanness  of  the  Machines.  Frequent  cleaning  of  the  ma- 
chines with  the  removal  of  all  the  old  lubricant  from  all  parts  of 
the  machine  is  essential. 

3.  Addition  of  Disinfectants  or  Antiseptics  to  the  Lubricants.— 
Various  antiseptics,  carbolic  acid  (1  per  cent,  to  2  per  cent.) 
being  the  most  common,  have  been  added  to  the  lubricant  to  pre- 
vent rashes,  and  in  the  case  of  cutting  emulsions  0.5  per  cent, 
of  disinfectants  soluble  in  water  have  been  used  for  this  purpose. 
The  results  obtained  have  not  been  altogether  satisfactory,  and 
reliance  cannot  be  placed  upon  such  a  method  to  prevent  skin 
rashes. 

4.  Sterilization  by  Heat. — It  has  been  suggested  to  heat  the 
cutting  oil  to  300°F.  for  a  short  period  with  a  view  to  sterilizing 
it  as  well  as  to  increase  its  antiseptic  or  germicidal  action. 

Laboratory  experiments  in  America  have  shown  that  used 
oil  possesses  rather  marked  germicidal  effects,  and  in  view  of  the 
fact  that  the  used  oil  becomes  heated  during  use  attempts  were 
made  to  determine  whether  heating  new  oil  would  also  bestow 
upon  it  germicidal  powers.  Apparently,  heating  does  produce 
such  a  change,  but  the  temperature  required  is  upwards  of  125°C. 
The  actual  temperature  rquired  to  produce  this  germicidal  ac- 
tion in  the  oil  has  not  yet  been  determined,  but  it  has  been  recom- 
mended to  mix  new  oil  with  the  used  oil  before  filtering  and  heating, 
so  that  the  new  oil  would  possess  to  some  extent  the  germicidal 
power  of  the  used  oil. 


602  PRACTICE  OF  LUBRICATION 

5.  Removal  of  Workers  with  Septic  Infection  of  the  Hands.— 

Workers  whose  hands  become  the  seat  of  septic  infection  should 
not  be  allowed  to  work  on  machines,  as  they  are  liable  to  infect 
the  oil  with  germs  and  so  infect  other  workers. 

6.  Treatment,     (a)  Folliculitis  Produced   by   Blocking   of  the 
Glands. — As  a  general  rule,  frequent  washing  with  soap  and 
hot  water  is  sufficient  to  produce  a  rapid  cure.     The  skin  may 
be  subsequently  dusted    with   zinc   oxide  and   starch  powder. 

It  has  been  found  that  where  this  is  insufficient  a  mild  anti- 
septic applied  on  lint  has  relieved  the  irritation  and  given  good 
results. 

(b)  Septic  Infection  of  the  Skin  due  to  Cuts. — Septic  infection 
should  be  treated  on  general  principles  by  the  application  of 
suitable  antiseptic  dressings. 

7.  Susceptibility. — Certain  individuals  appear  to  be  particu- 
larly susceptible  to  the  a'ction  of  lubricants.2     Such  persons  when 
found  should  be  removed  from  contact  with  oil. 

Author's  Note.2  Bad  health,  weakness  following  upon  illness,  delicate 
skin,  etc. 


INDEX 


Acid,  fatty,  16,  62 

petroleum,  61 

rosin,  62 

sulphuric,  61 
Acidity,  61 

Action,  electric,  222,  223 
Ash,  64 
Asphalt,  66 

blown,  10 
Atomization,  346-352,  397 

Bath,  grease,  132 
Bearings,  99-157 
Bearings,  ball  and  roller,  176-191 

ball,  180-184,  288 

construction  of,  99-101 

hot,  122,  123,  141,  142 

journal,  100 

Kingsbury,  174 

materials  for,  101-103 

Michell,  170-174 

oiling    systems    for,     107-115, 
125,  126 

operating  conditions  of,  104-107, 
125 

ring   oiling,    158-162,  195,  196 

stern  tube,  261,  262 

thrust,  100,  101,  166-175,  207, 
260,  261 

turbine,  204-21 1 

(workmanship),  103,  104 
Beaters,  359 
Bitumen,  10 
Box,  gear,  481,  483 

Cabinets,  oil,  308,  556,  557 

Calendars,  307,  539 

Can,  oil,  300,  308  • 

Capillarity,  58,  59 

Cars,  electric  street,  281-285 

mine,  320-328 
Castor,  17,  240,  252 
Cehtipoise,  49 
Chains,  156,  545 


Circulation,  force  feed,  114,  196, 
201,  243-248,  254,  258,  448, 
475,  478 

gravity  feed,  113,  201 
Coalcutters,  534 
Coalmines,  320-328,  533 
Cocoanut-oil,  19 
Collieries,  320-328,  533 
Color,  46 
Colza,  18 
Combers,  297,  314 
Compounds,  cutting,  573-576 

soluble,  573-576 
Compressors,  air,  402-416 

Diesel  air,  525-529 

refrigerator,  422-437 
Consumption,  cylinder  oil,  377 

Diesel  engine  oil,  523 

gas  engine  oil,  465,  466 

motor  cycle  oil,  487 

turbine  oil,  218 
Cooler,  oil,  196 
Cooling,  air,  404,  405 

(gas  engines),  452 
Cracking,  7 
Creeping  oil,  287 
Crude,  petroleum,  2-8 
Crushers,  tan,  149,  355 
Cup,  compression,  130 

mechanical  feed,  131,  278 

Stauffer,  129,  276 

tallow,  352 
Cycles,  motor,  484-488 

Density,  35 

Deposits,  air  compressor,  409-412 

automobile,  479-481 

boiler,  343-349 

Diesel  engine,  524 

gas  engine,  458-461 

gasolene  engine,  479-481,  487 

internal  combustion  engine/ 155 

motor  cycles,  487 

oil  engine,  507-509 


603 


604 


INDEX 


Deposits,  steam  cylinder,  363-368 

steam  engine,  253 

turbine,  219-230 
Dirt,  67 

Distillation,  6-8 
Distribution,  oil,  115,  556-558 
Drive,  chain,  483 

Elevators,  543 
Engines,  aero,  488-492 

air  operated,  418,  419,  421 

automobile,  472-498 

blowing,  402-416 

colliery  hoisting,  370-372 

Diesel,  514-531 

gas,  438-471 

gasolene,  472-498 

high  speed,  enclosed  type  steam, 

243-253 

kerosene  oil,  499-513 
marine  steam,  256-263,  373-376 
semi-Diesel,  499-513 
stationary,    open    type    steam, 

238-242,  312 
steam    (cylinders    and  vaKes), 

150-154,  329-401 
Stumpf  (uniflow),  372,  373 
Westinghouse,  248 
Willans,  248 

Evaporation,  41 
Expansion,  coefficient  of,  39 
Explosions,  air  compressor,  412-415 

crank  chamber,  254,  255 

transformer,  598 

Fats,  animal,  21,  23,  24 

solidified,  26,  27 

vegetable,  17,  24 
Feedwater,  oil  in,  334-341,  374 
Filters,  oil,  216-218,  550-553,    594- 

596 
Filtration,  air,  404,  405 

oil,  550 
Firepoint,  40 
Flashpoint,  40 
Fluorescence,  46 
Foaming,  oil,  160 
Frames,  cap,  302,  318 

doubling,  505 

drawing,  297 

flyer,  300-302,  317 


Frames,  intermediate,  297 

mule,  302 

ring,  298,  313,  315,  316 

roving,  297 

slabbing,  297 
Friction,  coefficient  of,  83,   84,  288 

fluid,  81-82,  124 

laws  of,  79-84 

semi-solid,  82,  123-124 

solid,  79-81 

Gas,  453-455 
Gears,  150,  156,  544 
Generators,  electric,  163 
Gill-boxes,  preparer,  295 
Glands,  packing,  361,  362 

turbine,  211-214 
Glue,  68 
Graphite  (see  also  Solid  Lubricants), 

29-31 

Gravity,  35-38 
Grease,  anti-rust,  10 

black  floating,  28 

cold  neck,  26 

consistency  of,  133 

cup,  25 

cylinder,  388 

fibre,  26 

gear,  28 

graphite,  26 

hot  neck,  27 

petroleum,  28 

purity  of,  133 

quality  of,  133 

railway  wagon,  27 

rosin,  27 

scented,  28 

white,  27,  388 

wool,  23 

yarn,  28 

Grooves,  oil,  115,  237,  241,  260,  292 
Guard,  dust,  271,  281 
Gumming,  63 

Heat,  frictional,  116 

specific,  43 
Hydrocarbons,  4 
Hydroextractors,  295,  307 

Impurities,  67-69,  219-221 
Injection,  timed  oil,  441,  521 


INDEX 


605 


Jelly,  petroleum,  9 
Kilns,  rotary,  540 

Lead,  white,  32 

Leakage,  oil,  160,  164,  250,  287 

Locomotives,  264-280,  391-401 

Looms,  306,  315 

Lubricants,   hall  and  roller  bearing, 

190,  191 

Colloidal  (see  under  Solid  Lubri- 
cants) 

cutting,  559-576,  600-602 
semi-solid,  25-28 
solid,  29-32,  134-157 
testing,  33-78 

Lubrication,  commutator,  164 
gas  engine,  461-471 
grease,  128,  275-278,  281 
mine  car,  320-328 
oil  film,  124 
oil-gasolene,  486 
railway  rolling  stock,   264-280 
semi,  82,  123,  124 
semi-solid,  128,  275-278,  281 
steam     cylinders     and    valves, 

329-401 

wheel  flange,  284,  235 
Lubricators,    hydrostatic,    353-355, 

370,  393,  394 

mechanical,  85,  98,  111,  131, 
257,  268,  269,  322,  355,  371, 
394-400,  408,  431,  440,  505 

Machinery,  printing,  541 

spinning,  298-305,  313 

textile,  294-319 

weaving,  305-307,  315 

woodworking,  541 
Machines,  bottle-making,  142 

carding,  296 

galvanizing,  142 

hosiery,  310,  311,  315 

lace-making,  142,  310 

paper,  538 

p.inting,  541 

refrigerating,  422-437 

testing,  69-75 
Materials,  bearing,  101-103 
Mica,  32 
Mills,  cement,  540 

flour,  540 


Mills,  paper,  537-540 

steel  and  tinplate,  532 
Mines,  535 
Motors,  electric,  163 


Oil,  oils,  air  compressor,  415.  4 
aniinal,  15,  21,  23,  24 
automobile,  493-498  ~ 
batching,  10,  305 
bearing,  127,  128,  239-242 
bloomless,  14 
car,  280 

castor,  17,  240,  252 
circulation,  236 
cocoanut,  19 
cod,  23 

cold  test  cylinder,  10 
cottonseed,  19 
cutting,  157,  559-576 
dark  cylinder,  9,  11 
dark  lubricating,  9,  13 
Diesel  engine,  529-531 
Dolphin  jaw,  22 
drying,  15 
dynamo,  165 
earthnut,  20 
filtered  cylinder,  9,  11 
fish,  23 

fixed  and  fats,  15-24 
gas  engine,  469-471 
gasolene  engine,  493-498 
gear,  498 

impurities  in,  67-69 
(in  boilers),  341-344,  375 
(in  emulsion),  335 
(in  suspension),  334 
lard,  21 
lather,  311 
linseed,  19 

loco  cylinder,  400,  401 
loom,  311 
lubricating,  8 
marine  steam  engine,  256 
medicinal  white,  14 
melon,  22 
Menhaden,  23 
motor,  165,  493-498 
mustard  seed,  20 
noatsfoot,  21 
neutral,  12 
non-drying,  15 


606 


INDEX 


Oils,  non-viscous,  low  setting  point, 
13 

oil-engine,  509-513 

olive,  19 

pale,  12 

palm,  palmkernel,  20 

peanut,  20 

porpoise  jaw,  22 

railway,  278-280 

rape,  18 

red,  11 

refrigerator,   433,  434,  436,  437 

rosin,  20 

seal,  22 

selection  of  bearing,  124-127 

semi-drying,  15 

shafting,  289 

shale,  10 

soap-thickened,  27 

solidified,  26,  27 

soluble,  573-576 

sperm,  22 

spindle,  311 

stainless,  308-312 

steam  cylinder,  388-391 

steam  engine  bearing,  242,  248, 
253 

switch,  599 
tallow,  21 

thrust  bearing,  174,  175 
transformer,  598,  599 
turbine,  235-237 
vegetable,  15,  17-20,  23,  24 
viscous,  low  setting  point,  13 
whale,  22 
white,  14 
wool,  305 

Oilers,  bottle,  109,  110,  125 
locomotive,  274,  276 
rope,  547 
shafting,  312 
sight  feed  drop,  110,  111,   194, 

408 

syphon,  108,  109,  125,  256,  273 
Oiliness,  66 

Oiling,  bath,  112,  298,  430 
chain,  159 
circulation,  113,  125,  201,  207, 

234,  235 

force  feed,  114,  196,  201,  243- 
248,  254,  258,  448,  475, 
478 


Oiling,  hand,  107,  108,  125,  256,  290, 

322 
pad,    112,   269,   281,   282,   290, 

291,  301 

ring,  112,  158-162,  195,  281 
splash,  112,  125,  248-253,  406, 

433,  448,  476,  478 
waste,  270-272,  282 
Olefines,  4 
Openers,  294 
Oxidation,  63 

Paraffins,  4 

Plants,  hydraulic,  542 

ice-making,  435,  436 

screening,  535 
Point,  melting,  46 

setting,  44 
Poise,  49 
Poiseulle,  48 
Poisoning,  oil,  600-602 
Presses,  filter,  594-596 
Pressure,  bearing,  105,  106 
Products,  petroleum,  8 
Protector,  oil  hole,  290 
Pumps,  dry  air  and  vacuum,  417 

hydraulic,  542 
Purification,  oil,  550-555,  594-596 

Quarries,  535 

Rape,  18 
Rape,  blown,  18 
Recovery,  oil,  550-555,  565-567 
Redistillation,  8 
Refining,  6 

Refrigerators,  422-437 
Resistance,  specific,  584 
Rings,  oil,  159-161 
Rollers,  top,  314 
Ropers,  driving,  549 
wire,  156,  546-549 

Saponification,  17 

Savealls,  287 

Saving,  power,  315-319 

Scutchers,  294 

Separators,   oil,    245-247,    337-340, 

374 

Shafting,  transmission,  286-289,  312 
Soap,  metallic,  17 
Softening,  feed  water,  341 


INDEX 


607 


Spindles,  Rabbeth,  299 
Spraying,  oil,  160,  164,  234 
Stains,  oil,  309-311 
Stamps,  pneumatic,  536 
Steam,  333,  334 

oil  in  exhaust,  334-341,  374 
Stonecrushers,  149,  535 
Storage,  oil,  556-558 
Strength,  dielectric,  584-587 
Suet,  538,  539 
Sulphur,  flowers  of,  32 
Sunbleaching,  9 
Switches,  oil,  597,  598 
Syphoning,  59 
Systems,  oil,  107-115 

Talc,  31 

Tallow,  21,  387,  388 

Tanks,  settling,  216,  218 

Tar,  66 

Temperature,  bearing,  106 

f  Fictional,  116 

spontaneous  ignition,  413 
Tension,  surface,  61 
Tests,  carbon  residue,  64-66 

chemical,  61-69,  385-387 

cloud,  44 

cold,  44 

distillation,  42 

dynamometer,  74—75 

electrical,  75-76 

emulsification,  59-60 

free  revolution,  77 

gas  engine,  76 

mechanical,  69-78 

pour,  44 

physical,  35-61,  385-387 

steam  engine,  76 

temperature,  72-74 
Tester,  Lahmeyer  oil,  70 


Tester,  Thurston  oil,  71 
Testing,  mechanical,  69-78 
Throwing,  oil,  164 
Tintometers,  47 
Tools,  machine,  290-293 

pneumatic,  420-421 
Tractors,  agricultural,  492-493 
Transference,  thermal,  590 
Transformers,  electrical,  577-598 
Traveller,  314 
Troubles,  bearing,  117-122 
Turbines,  Curtiss,  230-235 

geared,  192,  193,  214,  215,  237 

steam,  192-237 
Value,  iodine,  62 

saponification,  62 
Valves,  Corliss,    357,    368-370,    407 

drop,  358 

piston,  357 

poppet,  358 

slide,  356 
Vaseline,  10 
Viscometer,  Engler,  50,  54 

Michell,  51,  52 

Ostwald,  49 

Redwood,  50,  54 

Saybolt,  50,  55 
Viscosity,  24,  48-58 

absolute,  48-51 

(conversion  tables),  53—55 

(fixed  oils  and  fats),  24 

(semi-solid  lubricants),  58 
Volatility,  41 

Water,  68,  69,  220,  221 
Wax,  5,  9,  10 
Wear,  209,  283 
Wells,  oil,  1 
Wheels,  gear,   284 
Works,  cement,  540 


UBRAEV 


Return  to  desk  from 


Library 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


